scholarly journals Further Observations on the Nuclear Envelope of the Animal Cell

1959 ◽  
Vol 6 (2) ◽  
pp. 147-156 ◽  
Author(s):  
Michael L. Watson
Keyword(s):  
Electron Microscope ◽  
Nuclear Envelope ◽  
Cross Section ◽  
Cross Sections ◽  
Nuclear Membrane ◽  
Animal Cell ◽  
Nuclear Surface ◽  
Apparent Discrepancy ◽  
Outer Nuclear Membrane ◽  
Direct Association

The term pore complex is proposed for approximately cylindrical formations which are observed with the electron microscope to penetrate the nuclear envelope of cells. Cross-sections of the pore complex are somewhat annular in shape, but differ in appearance depending upon the level of the cross-section with respect to the nuclear surface. An explanation is offered for the apparent discrepancy between the width of pores in sections perpendicular to the nuclear envelope and the width of cross-sections of the pore complex in tangential sections. Channels associated with the pore complex extend deep into the nucleus. Although crescents and spirals of ribonucleoprotein particles were often seen in the immediate vicinity of the outer nuclear membrane, direct association with the pore complex was not observed. Many examples were found of pores that were not covered by a continuous membrane although the possibility of such a covering in some cases is not precluded.

scholarly journals Endoplasmic reticulum-to-Golgi transitions upon herpes virus infection

F1000Research ◽  
2018 ◽  
Vol 6 ◽  
pp. 1804 ◽  
Author(s):  
Peter Wild ◽  
Andres Kaech ◽  
Elisabeth M. Schraner ◽  
Ladina Walser ◽  
Mathias Ackermann
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Golgi Complex ◽  
Nuclear Membrane ◽  
Progeny Virus ◽  
Cytoplasmic Matrix ◽  
Outer Nuclear Membrane ◽  
Nuclear Membranes ◽  
Perinuclear Space ◽  
Hsv 1

Background: Herpesvirus capsids are assembled in the nucleus, translocated to the perinuclear space by budding, acquiring tegument and envelope, or released to the cytoplasm via impaired nuclear envelope. One model proposes that envelopment, “de-envelopment” and “re-envelopment” is essential for production of infectious virus. Glycoproteins gB/gH were reported to be essential for de-envelopment, by fusion of the “primary” envelope with the outer nuclear membrane. Yet, a high proportion of enveloped virions generated from genomes with deleted gB/gH were found in the cytoplasm and extracellular space, suggesting the existence of alternative exit routes.Methods: We investigated the relatedness between the nuclear envelope and membranes of the endoplasmic reticulum and Golgi complex, in cells infected with either herpes simplex virus 1 (HSV-1) or a Us3 deletion mutant thereof, or with bovine herpesvirus 1 (BoHV-1) by transmission and scanning electron microscopy, employing freezing technique protocols.Results:  The Golgi complex is a compact entity in a juxtanuclear position covered by a membrane on thecisface. Golgi membranes merge with membranes of the endoplasmic reticulum forming an entity with the perinuclear space. All compartments contained enveloped virions. After treatment with brefeldin A, HSV-1 virions aggregated in the perinuclear space and endoplasmic reticulum, while infectious progeny virus was still produced.Conclusions: The data suggest that virions derived by budding at nuclear membranes are intraluminally transported from the perinuclear space via Golgi -endoplasmic reticulum transitions into Golgi cisternae for packaging. Virions derived by budding at nuclear membranes are infective like Us3 deletion mutants, which  accumulate in the perinuclear space. Therefore, i) de-envelopment followed by re-envelopment is not essential for production of infective progeny virus, ii) the process taking place at the outer nuclear membrane is budding not fusion, and iii) naked capsids gain access to the cytoplasmic matrix via impaired nuclear envelope as reported earlier.

scholarly journals Proteins transported in slow components a and b of axonal transport are distributed differently in the transverse plane of the axon.

1985 ◽  
Vol 100 (4) ◽  
pp. 1167-1172 ◽  
Author(s):  
K Heriot ◽  
P Gambetti ◽  
R J Lasek
Keyword(s):  
Electron Microscope ◽  
Axonal Transport ◽  
Cross Section ◽  
Cross Sections ◽  
Polyacrylamide Gel Electrophoresis ◽  
Transverse Plane ◽  
Hypoglossal Nucleus ◽  
Electron Microscope Autoradiography ◽  
Microscope Autoradiography ◽  
Slow Transport

The distribution of the proteins migrating with the slow components a (SCa) and b (SCb) of axonal transport were studied in cross-sections of axons with electron microscope autoradiography. Radiolabeled amino acids were injected into the hypoglossal nucleus of rabbits and after 15 d, the animals were killed. Hypoglossal nerves were processed either for SDS-polyacrylamide gel electrophoresis fluorography to identify and locate the two components of slow transport, or for quantitative electron microscope autoradiography. Proteins transported in SCa were found to be uniformly distributed within the cross-section of the axon. Labeled SCb proteins were also found throughout the axonal cross-section, but the subaxolemmal region of the axon contained 2.5 times more SCb radioactivity than any comparable area in the remainder of the axon.

Energy Loss Imaging in Biology

1982 ◽  
Vol 40 ◽  
pp. 416-419
Author(s):  
H. Shuman ◽  
A.V. Somlyo ◽  
A.P. Somlyo ◽  
T. Frey ◽  
D. Safer
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Cross Section ◽  
Cross Sections ◽  
Count Rate ◽  
Electron Flux ◽  
Characteristic Energy ◽  
Spectrometer Slit ◽  
Electron Energy Loss ◽  
Sensitive Method

It has been recognized for sometime that electron energy loss spectroscopy (EELS) is potentially the most sensitive method of measuring elemental composition in the electron microscope. Magnetic sector spectrometers currently in use collect most of the inelastically scattered electrons, while the cross sections for ionization of the L2 3 levels of the biologically important elements are large. The energies of the theoretically predicted L2 3 absorption edge maxima and their corresponding differential cross section for lOmrad collection and 80keV incident electrons are shown in Table I. The characteristic energy loss electron count rate expected from one atom with lOeV spectrometer slit width and lOOA/cm2 (the maximum available from a tungsten hairpin) electron flux at the specimen, indicates that the minimum detectable mass sensitivity of EELS will be high. An experimentally determined count rate and cross section for the Fe M2, 3 edge was determined from the ferritin images shown in Fig. 1.

Association of membrane cisternae and macrotubules in vinblastine-treated histiocytes

1977 ◽  
Vol 28 (1) ◽  
pp. 273-281
Author(s):  
M. Schliwa
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Cichlid Fish ◽  
Entire Length ◽  
Tubular Structures ◽  
Outer Nuclear Membrane ◽  
Unusual Association ◽  
Pterophyllum Scalare

Resting histiocytes within the dermis and epidermis of the cichlid fish Pterophyllum scalare exhibit an unusual association between stacks of lamellar cisternae and tubular structures greater in diameter than ordinary microtubules (macrotubules) after treatment with 2 × 10(−4) M vinblastine. Macrotubules are found in the intercisternal spaces in a regular side-by-side orientation and extend the entire length of the cisternae. The lamellae seem to be formed as a result of increased membrane proliferation of the outer nuclear membrane; in some instances, cisternae have been observed to be continuous with the nuclear envelope. Since blebbing of the outer nuclear membrane is also observed in untreated histiocytes, lamellae formation is envisaged as hypertrophy of a normally occurring process. The association of lamellae with macrotubules possibly indicates a relationship between membranes and microtubule proteins.

scholarly journals Outer nuclear membrane protein Kuduk modulates the LINC complex and nuclear envelope architecture

2017 ◽  
Vol 216 (9) ◽  
pp. 2827-2841 ◽  
Author(s):  
Zhao-Ying Ding ◽  
Ying-Hsuan Wang ◽  
Yu-Cheng Huang ◽  
Myong-Chol Lee ◽  
Min-Jen Tseng ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Control Mechanism ◽  
Genetic Data ◽  
Linc Complex ◽  
Outer Nuclear Membrane ◽  
Functional Conservation ◽  
Evolutionarily Conserved ◽  
Human Orthologue ◽  
Quality Control Mechanism

Linker of nucleoskeleton and cytoskeleton (LINC) complexes spanning the nuclear envelope (NE) contribute to nucleocytoskeletal force transduction. A few NE proteins have been found to regulate the LINC complex. In this study, we identify one, Kuduk (Kud), which can reside at the outer nuclear membrane and is required for the development of Drosophila melanogaster ovarian follicles and NE morphology of myonuclei. Kud associates with LINC complex components in an evolutionarily conserved manner. Loss of Kud increases the level but impairs functioning of the LINC complex. Overexpression of Kud suppresses NE targeting of cytoskeleton-free LINC complexes. Thus, Kud acts as a quality control mechanism for LINC-mediated nucleocytoskeletal connections. Genetic data indicate that Kud also functions independently of the LINC complex. Overexpression of the human orthologue TMEM258 in Drosophila proved functional conservation. These findings expand our understanding of the regulation of LINC complexes and NE architecture.

scholarly journals ELECTRON MICROSCOPY OF BASOPHILIC STRUCTURES OF SOME INVERTEBRATE OOCYTES

1956 ◽  
Vol 2 (1) ◽  
pp. 93-104 ◽  
Author(s):  
Lionel I. Rebhun
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Nuclear Envelope ◽  
Cross Sections ◽  
Dense Material ◽  
Continuous Space ◽  
Surf Clam ◽  
Surface View ◽  
Hexagonal Pattern

Highly basophilic plate-shaped regions from oocytes of the surf clam have been examined with the electron microscope. The regions are composed of flat, hollow vesicles perforated by pores arranged, in surface view, in a hexagonal pattern. Cross-sections of this structure show a periodicity consisting of loops (cross-sections of the continuous space within the vesicle) alternating with spaces partly filled with dense material (pores). These structures are shown to resemble closely, the nuclear envelope. Similarities to and differences from basophilic regions of other cells are discussed and it is suggested that the small granules of Palade (38) are represented by granules composing the walls of the annuli of the nuclear envelope and assumed to be present in the annuli of the vesicles. Because of differences in the structure of these regions from basophilic regions of other cells, the name periodic lamellae is suggested since the structures show periodically repeating substructures (annuli) in both cross-sections and surface views.

scholarly journals Novel plant SUN–KASH bridges are involved in RanGAP anchoring and nuclear shape determination

2012 ◽  
Vol 196 (2) ◽  
pp. 203-211 ◽  
Author(s):  
Xiao Zhou ◽  
Katja Graumann ◽  
David E. Evans ◽  
Iris Meier
Keyword(s):  
Muscular Dystrophy ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Epidermal Cells ◽  
Nuclear Shape ◽  
Interacting Proteins ◽  
Outer Nuclear Membrane ◽  
Plant Kingdom ◽  
Inner Nuclear Membrane ◽  
Shape Determination

Inner nuclear membrane Sad1/UNC-84 (SUN) proteins interact with outer nuclear membrane (ONM) Klarsicht/ANC-1/Syne homology (KASH) proteins, forming linkers of nucleoskeleton to cytoskeleton conserved from yeast to human and involved in positioning of nuclei and chromosomes. Defects in SUN–KASH bridges are linked to muscular dystrophy, progeria, and cancer. SUN proteins were recently identified in plants, but their ONM KASH partners are unknown. Arabidopsis WPP domain–interacting proteins (AtWIPs) are plant-specific ONM proteins that redundantly anchor Arabidopsis RanGTPase–activating protein 1 (AtRanGAP1) to the nuclear envelope (NE). In this paper, we report that AtWIPs are plant-specific KASH proteins interacting with Arabidopsis SUN proteins (AtSUNs). The interaction is required for both AtWIP1 and AtRanGAP1 NE localization. AtWIPs and AtSUNs are necessary for maintaining the elongated nuclear shape of Arabidopsis epidermal cells. Together, our data identify the first KASH members in the plant kingdom and provide a novel function of SUN–KASH complexes, suggesting that a functionally diverged SUN–KASH bridge is conserved beyond the opisthokonts.

scholarly journals Nuclear surface complex as observed with the high resolution scanning electron microscope. Visualization of the membrane surfaces of the neclear envelope and the nuclear cortex from Xenopus laevis oocytes

1978 ◽  
Vol 77 (2) ◽  
pp. 517-535 ◽  
Author(s):  
G Schatten ◽  
M Thoman
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Scanning Electron Microscope ◽  
Nuclear Envelope ◽  
Xenopus Laevis Oocytes ◽  
Nuclear Surface ◽  
Surface Complex ◽  
Membrane Surfaces ◽  
Pore Complexes ◽  
Scanning Electron

The nuclear envelope and associated structures from Xenopus laevis oocytes (stage VI) have been examined with the high resolution scanning electron microscope (SEM). The features of the inner and outer surfaces of the nuclear surface complex were revealed by manual isolation , whereas the membranes facing the perinuclear space (the space between the inner and outer nuclear membranes) were observed by fracturing the nuclear envelope in this plane and splaying the corresponding regions apart. Pore complexes were observed on all four membrane surfaces of this double-membraned structure. The densely packed pore complexes (55/micron2) are often clustered into triplets with shared walls (outer diameter = 90 nm; inner diameter = 25 nm; wall thickness = aproximately 30 nm), and project aproximately 20 nm above each membrane except where they are flush with the innermost surface. The pore complex appears to be an aggregate of four 30-nm subunits. The nuclear cortex, a fibrous layer (300 nm thickness) associated with the inner surface of the nuclear envelope, has been revealed by rapid fixation. This cortical layer is interrupted by funnel-shaped intranuclear channels (120-640 nm diam) which narrow towards the pore complexes. Chains of particles, arranged in spirals, are inserted into these intranuclear channels. The fibers associated with the innermost face of the nuclear envelope can be extraced with 0.6 MKI to reveal the pore complexes. A model of the nuclear surface complex, compiled from the visualization of all the membrane faces and the nuclear cortex, demonstrates relations between the intranuclear channels (3.2/micron2) and the numerous pore complexes, and the possibility of their role in nucleocytoplasmic interactions.

scholarly journals Atg39 selectively captures inner nuclear membrane into lumenal vesicles for delivery to the autophagosome

2021 ◽  
Author(s):  
Sunandini Chandra ◽  
Philip J. Mannino ◽  
David J. Thaller ◽  
Nicholas R. Ader ◽  
Megan C. King ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Electron Tomography ◽  
Membrane Remodeling ◽  
Outer Nuclear Membrane ◽  
Inner Nuclear Membrane ◽  
Gfp Reporter ◽  
Sequence Elements ◽  
Lumenal Domain

AbstractMechanisms that turnover components of the nucleus and inner nuclear membrane (INM) remain to be fully defined. We explore how components of the INM are selected by a cytosolic autophagy apparatus through a transmembrane nuclear envelope-localized cargo adaptor, Atg39. A split-GFP reporter shows that Atg39 localizes to the outer nuclear membrane (ONM) and thus targets the INM across the nuclear envelope lumen. Consistent with this, sequence elements that confer both nuclear envelope localization and a membrane remodeling activity are mapped to the Atg39 lumenal domain; these lumenal motifs are required for the autophagy-mediated degradation of an integral INM protein. Interestingly, correlative light and electron tomography shows that the overexpression of Atg39 leads to the expansion of the ONM and the enclosure of a network of INM-derived vesicles in the nuclear envelope lumen. Thus, we propose an outside-in model of nucleophagy where INM is delivered into vesicles in the nuclear envelope lumen, which can be targeted by the autophagosome.

scholarly journals UNC-83 Is a KASH Protein Required for Nuclear Migration and Is Recruited to the Outer Nuclear Membrane by a Physical Interaction with the SUN Protein UNC-84

2006 ◽  
Vol 17 (4) ◽  
pp. 1790-1801 ◽  
Author(s):  
Matthew D. McGee ◽  
Regina Rillo ◽  
Amy S. Anderson ◽  
Daniel A. Starr
Keyword(s):  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Mammalian Cells ◽  
Protein Targeting ◽  
Point Mutations ◽  
Nuclear Migration ◽  
Physical Interaction ◽  
The Sun ◽  
Outer Nuclear Membrane

UNC-84 is required to localize UNC-83 to the nuclear envelope where it functions during nuclear migration. A KASH domain in UNC-83 was identified. KASH domains are conserved in the nuclear envelope proteins Syne/nesprins, Klarsicht, MSP-300, and ANC-1. Caenorhabditis elegans UNC-83 was shown to localize to the outer nuclear membrane and UNC-84 to the inner nuclear membrane in transfected mammalian cells, suggesting the KASH and SUN protein targeting mechanisms are conserved. Deletion of the KASH domain of UNC-83 blocked nuclear migration and localization to the C. elegans nuclear envelope. Some point mutations in the UNC-83 KASH domain disrupted nuclear migration, even if they localized normally. At least two separable portions of the C-terminal half of UNC-84 were found to interact with the UNC-83 KASH domain in a membrane-bound, split-ubiquitin yeast two-hybrid system. However, the SUN domain was essential for UNC-84 function and UNC-83 localization in vivo. These data support the model that KASH and SUN proteins bridge the nuclear envelope, connecting the nuclear lamina to cytoskeletal components. This mechanism seems conserved across eukaryotes and is the first proposed mechanism to target proteins specifically to the outer nuclear membrane.

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