scholarly journals Mechanical principles of nuclear shaping and positioning

2018 ◽  
Vol 217 (10) ◽  
pp. 3330-3342 ◽  
Author(s):  
Tanmay P. Lele ◽  
Richard B. Dickinson ◽  
Gregg G. Gundersen
Keyword(s):  
Nuclear Envelope ◽  
Mechanical Response ◽  
Mechanical Resistance ◽  
Nuclear Surface ◽  
Nuclear Movement ◽  
Large Size ◽  
Force Transfer ◽  
Nuclear Shaping ◽  
Resistance To Deformation ◽  
Cellular Forces

Positioning and shaping the nucleus represents a mechanical challenge for the migrating cell because of its large size and resistance to deformation. Cells shape and position the nucleus by transmitting forces from the cytoskeleton onto the nuclear surface. This force transfer can occur through specialized linkages between the nuclear envelope and the cytoskeleton. In response, the nucleus can deform and/or it can move. Nuclear movement will occur when there is a net differential in mechanical force across the nucleus, while nuclear deformation will occur when mechanical forces overcome the mechanical resistance of the various structures that comprise the nucleus. In this perspective, we review current literature on the sources and magnitude of cellular forces exerted on the nucleus, the nuclear envelope proteins involved in transferring cellular forces, and the contribution of different nuclear structural components to the mechanical response of the nucleus to these forces.

Association of cytoplasmic dynein with manchette microtubules and spermatid nuclear envelope during spermiogenesis in rats

1994 ◽  
Vol 107 (3) ◽  
pp. 625-633 ◽  
Author(s):  
T. Yoshida ◽  
S.O. Ioshii ◽  
K. Imanaka-Yoshida ◽  
K. Izutsu
Keyword(s):  
Nuclear Envelope ◽  
Mature Spermatozoon ◽  
Cytoplasmic Dynein ◽  
Bovine Brain ◽  
Nuclear Surface ◽  
Double Immunofluorescence ◽  
Nuclear Shaping ◽  
Spermatid Nucleus ◽  
Microtubular Network ◽  
Inner Region

During spermiogenesis, the shape of the spermatid nucleus, which is spherical, changes and it becomes the sperm head. A microtubular structure called a manchette is thought to be involved in this morphogenetic process. In this report, we demonstrate the localization of cytoplasmic dynein and manchette development by a double immunofluorescence technique using anti-bovine brain MAP 1C and anti-tubulin. Before step 6 of the Leblond and Clermont staging, the microtubules showed a fine reticular network, and the dynein staining was homogeneous. In step 6, the microtubular network was concentrated around the nucleus. The manchette developed in step 7 spermatids, and was fully formed, with a skirt-like appearance, covering the nuclear surface in step 8. Dynein fluorescence was associated with the microtubular manchette in steps 7–10. During these steps, the nucleus was protruded from the cytoplasm. In steps 11–13, the most active stages in nuclear shaping, the dynein was densely localized at the nuclear surface covered by the manchette. As the nucleus acquired a shape similar to the mature spermatozoon at step 14, the dynein fluorescence was localized only at the concave side of the nuclear caudal edge. The manchette became narrower and elongated. In step 15, the manchette extended into the elongated cytoplasm, diminishing during steps 16–18. The localization of the dynein was limited to the ventral aspect of the caudal head in these steps. There was little dynein fluorescence in mature spermatozoa. Immunoelectron microscopy showed positive reactions in the nuclear envelope and the inner region of the microtubular manchette. These observations suggest that cytoplasmic dynein, possibly bound to the nuclear envelope, and manchette microtubules are involved in the protrusion of the spermatid nucleus from the cytoplasm.

Detection and mapping of interactions between chromatin and the nuclear envelope in drosophila embryos

1995 ◽  
Vol 53 ◽  
pp. 764-765
Author(s):  
W.F. Marshall ◽  
A.F. Dernburg ◽  
B. Harmon ◽  
J.W. Sedat
Keyword(s):  
Nuclear Envelope ◽  
Chromatin Condensation ◽  
Three Dimensional ◽  
Physiological Role ◽  
Nuclear Surface ◽  
Intact Cells ◽  
Molecular Determinants ◽  
Surface Harmonic ◽  
Drosophila Embryos

Interactions between chromatin and nuclear envelope (NE) have been implicated in chromatin condensation, gene regulation, nuclear reassembly, and organization of chromosomes within the nucleus. To further investigate the physiological role played by such interactions, it will be necessary to determine which loci specifically interact with the nuclear envelope. This will not only facilitate identification of the molecular determinants of this interaction, but will also allow manipulation of the pattern of chromatin-NE interactions to probe possible functions. We have developed a microscopic approach to detect and map chromatin-NE interactions inside intact cells.Fluorescence in situ hybridization (FISH) is used to localize specific chromosomal regions within the nucleus of Drosophila embryos and anti-lamin immunofluorescence is used to detect the nuclear envelope. Widefield deconvolution microscopy is then used to obtain a three-dimensional image of the sample (Fig. 1). The nuclear surface is represented by a surface-harmonic expansion (Fig 2). A statistical test for association of the FISH spot with the surface is then performed.

scholarly journals Immunochemical and immunocytochemical identification of a myosin heavy chain polypeptide in Nicotiana pollen tubes

1989 ◽  
Vol 92 (4) ◽  
pp. 569-574
Author(s):  
X.J. Tang ◽  
P.K. Hepler ◽  
S.P. Scordilis
Keyword(s):  
Pollen Tube ◽  
Nuclear Envelope ◽  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Immunofluorescence Microscopy ◽  
Generative Cell ◽  
Pollen Tubes ◽  
Nuclear Surface ◽  
Common Pattern ◽  
Western Blots

A myosin heavy chain polypeptide has been identified and localized in Nicotiana pollen tubes using monoclonal anti-myosin antibodies. The epitopes of these antibodies were found to reside on the myosin heavy chain head and rod portion and were, therefore, designated anti-S-1 (myosin S-1) and anti-LMM (light meromyosin). On Western blots of the total soluble pollen tube proteins, both anti-S-1 and anti-LMM label a polypeptide of approximately 175,000 Mr. Immunofluorescence microscopy shows that both antibodies yield numerous fluorescent spots throughout the whole length of the tube, often with an enrichment in the tube tip. These fluorescent spots are thought to represent vesicles and/or organelles in the pollen tubes. In addition to this common pattern, anti-S-1 stains both the generative cell and the vegetative nuclear envelope. The different staining patterns of the nucleus between anti-S-1 and anti-LMM may be caused by some organization and/or anchorage state of the myosin molecules on the nuclear surface that differs from those on the vesicles and/or organelles.

scholarly journals Monoclonal antibodies identify a group of nuclear pore complex glycoproteins.

1987 ◽  
Vol 104 (5) ◽  
pp. 1143-1156 ◽  
Author(s):  
C M Snow ◽  
A Senior ◽  
L Gerace
Keyword(s):  
Monoclonal Antibodies ◽  
Nuclear Envelope ◽  
Nuclear Pore Complex ◽  
Peptide Mapping ◽  
Polyclonal Antibodies ◽  
Integral Membrane Protein ◽  
Nucleocytoplasmic Transport ◽  
Nuclear Pore ◽  
Nuclear Surface ◽  
Punctate Pattern

Using monoclonal antibodies we identified a group of eight polypeptides of rat liver nuclear envelopes that have common epitopes. Most or all of these proteins are structurally distinct, as shown by tryptic peptide mapping and analysis with polyclonal antibodies. While these polypeptides are relatively tightly bound to nuclear membranes, only one is an integral membrane protein. The eight antigens cofractionate with the nuclear pore complex under various conditions of ionic strength and detergent. It can be seen by immunofluorescence microscopy that the monoclonal antibodies reacting with these antigens stain the nuclear surface of interphase cells in a finely punctate pattern. When the nuclear envelope is disassembled and subsequently reformed during mitosis, the proteins are reversibly dispersed throughout the cytoplasm in the form of minute foci. By EM immunogold localization on isolated nuclear envelopes, the monoclonal antibodies label exclusively the nuclear pore complex, at both its nucleoplasmic and cytoplasmic margins. Considered together, our biochemical and localization data indicate that the eight nuclear envelope polypeptides are pore complex components. As shown in the accompanying paper (Holt, G. D., C. M. Snow, A. Senior, R. S. Haltiwanger, L. Gerace, and G. W. Hart, J. Cell Biol., 104:1157-1164) these eight polypeptides contain a novel form of glycosylation, O-linked N-acetylglucosamine. The relative abundance and disposition of these O-linked glycoproteins in the pore complex are consistent with their having a role in nucleocytoplasmic transport.

scholarly journals Magnetic measurement system of sandy gravel specimens shape during tests in a large triaxial apparatus

2019 ◽  
Vol 92 ◽  
pp. 02004
Author(s):  
Roberta Ventini ◽  
Alessandro Flora ◽  
Stefania Lirer ◽  
Claudio Mancuso
Keyword(s):  
Relative Humidity ◽  
Mechanical Response ◽  
Magnetic Measurement ◽  
Triaxial Tests ◽  
Sandy Gravel ◽  
Partially Saturated ◽  
Triaxial Apparatus ◽  
Large Size ◽  
Size Of Particles ◽  
The University

As well known, rockfill behaviour is strongly influenced by both intrinsic (mineralogy and size of particles, grain shapes, soil grading etc.) and state parameters (relative density, stress state, relative humidity). To investigate their mechanical response to stresses and relative humidity (RH) loadings, a large size triaxial device (H = 410 mm, D = 200 mm) has been developed at the University of Naples Federico II (Italy), including modifications required to impose partially saturated conditions in the specimen by means of the vapour equilibrium technique. In order to evaluate local axial and radial strains and global volumetric strains in partially saturated conditions, a magnetic shape detector device has been designed and installed. The accuracy of this system has been evaluated in some isotropic compression triaxial tests on compacted sandy-gravel specimens. The experimental data clearly show the effectiveness of the magnetic system in the measurement of axial displacements while the measurement in radial direction appear to be strongly affected by the non-linearity of the complex magnetic field generated during the test and requires further checking tests.

scholarly journals Effect of Inclusions on the Corrosion Properties of the Nickel-Based Alloys 718 and EP718

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1177 ◽  
Author(s):  
Ekaterina Alekseeva ◽  
Andrey Karasev ◽  
Pär G. Jönsson ◽  
Aleksey Alkhimenko
Keyword(s):  
Corrosion Resistance ◽  
Alloy 718 ◽  
Corrosion Properties ◽  
Electrolytic Extraction ◽  
Operational Conditions ◽  
Large Size ◽  
Size Number ◽  
Resistance To Deformation ◽  
The Given ◽  
Harmful Effects

Inclusions in steels and alloys are known to lower the resistance to deformation, as well as to lower the mechanical, corrosion and other properties. Studies of inclusions in nickel-based alloys are important since these materials could suffer from corrosion degradation in harsh operational conditions. This, in fact, could lead to a pitting initiation around the inclusions. Two industrial Ni-based alloys (alloy 718 and EP718) were investigated to determine the harmful effects of different inclusions on the corrosion resistance of Ni-based alloys. Specifically, the inclusion characteristics (such as composition, morphology, size, number and location) were determined for inclusions collected on film filters after electrolytic extraction and dissolution of a metal matrix around different inclusions on surfaces of metal samples after electrolytic extraction (EE). It was found that both Ni-based alloys contain various inclusion types: carbides (large size NbTi-C and small multicomponent carbides), nitrides TiNb-N and sulphides (TiNb-S in EP718 alloy). The most harmful effects on the corrosion resistance of metal were detected around sulphides and small carbides containing Mo, W, Cr. Dissolution effects were also observed around large carbides and nitrides, especially around inclusions larger than 10 µm. Moreover, the dissolution of a matrix around inclusions and clusters located on the grain boundaries were found to be 2.1–2.7 times larger compared to inclusions found inside of grains of the given alloy samples.

scholarly journals Interphase Nuclei of Many Mammalian Cell Types Contain Deep, Dynamic, Tubular Membrane-bound Invaginations of the Nuclear Envelope

1997 ◽  
Vol 136 (3) ◽  
pp. 531-544 ◽  
Author(s):  
Mark Fricker ◽  
Michael Hollinshead ◽  
Nick White ◽  
David Vaux
Keyword(s):  
Nuclear Envelope ◽  
Time Lapse ◽  
Cell Types ◽  
Live Cells ◽  
Nuclear Pore ◽  
Nuclear Pore Complexes ◽  
Nuclear Surface ◽  
Topological Features ◽  
Cytoplasmic Transport ◽  
Pore Complexes

The nuclear envelope consists of a doublemembraned extension of the rough endoplasmic reticulum. In this report we describe long, dynamic tubular channels, derived from the nuclear envelope, that extend deep into the nucleoplasm. These channels show cell-type specific morphologies ranging from single short stubs to multiple, complex, branched structures. Some channels transect the nucleus entirely, opening at two separate points on the nuclear surface, while others terminate at or close to nucleoli. These channels are distinct from other topological features of the nuclear envelope, such as lobes or folds. The channel wall consists of two membranes continuous with the nuclear envelope, studded with features indistinguishable from nuclear pore complexes, and decorated on the nucleoplasmic surface with lamins. The enclosed core is continuous with the cytoplasm, and the lumenal space between the membranes contains soluble ER-resident proteins (protein disulphide isomerase and glucose-6-phosphatase). Nuclear channels are also found in live cells labeled with the lipophilic dye DiOC6. Time-lapse imaging of DiOC6-labeled cells shows that the channels undergo changes in morphology and spatial distribution within the interphase nucleus on a timescale of minutes. The presence of a cytoplasmic core and nuclear pore complexes in the channel walls suggests a possible role for these structures in nucleo–cytoplasmic transport. The clear association of a subset of these structures with nucleoli would also be consistent with such a transport role.

scholarly journals Samp1 Mislocalization in Emery-Dreifuss Muscular Dystrophy

Cells ◽  
2018 ◽  
Vol 7 (10) ◽  
pp. 170 ◽  
Author(s):  
Elisabetta Mattioli ◽  
Marta Columbaro ◽  
Mohammed Hakim Jafferali ◽  
Elisa Schena ◽  
Einar Hallberg ◽  
...  
Keyword(s):  
Muscular Dystrophy ◽  
Membrane Protein ◽  
Nuclear Envelope ◽  
Muscle Cell ◽  
Nuclear Periphery ◽  
Linc Complex ◽  
Cell Nuclei ◽  
Nuclear Movement ◽  
Prelamin A ◽  
Human Myotubes

LMNA linked-Emery-Dreifuss muscular dystrophy (EDMD2) is a rare disease characterized by muscle weakness, muscle wasting, and cardiomyopathy with conduction defects. The mutated protein lamin A/C binds several nuclear envelope components including the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex and the inner nuclear membrane protein Samp1 (Spindle Associated Membrane Protein 1). Considering that Samp1 is upregulated during muscle cell differentiation and it is involved in nuclear movement, we hypothesized that it could be part of the protein platform formed by LINC proteins and prelamin A at the myotube nuclear envelope and, as previously demonstrated for those proteins, could be affected in EDMD2. Our results show that Samp1 is uniformly distributed at the nuclear periphery of normal human myotubes and committed myoblasts, but its anchorage at the nuclear poles is related to the presence of farnesylated prelamin A and it is disrupted by the loss of prelamin A farnesylation. Moreover, Samp1 is absent from the nuclear poles in EDMD2 myotubes, which shows that LMNA mutations associated with muscular dystrophy, due to reduced prelamin A levels in muscle cell nuclei, impair Samp1 anchorage. Conversely, SUN1 pathogenetic mutations do not alter Samp1 localization in myotubes, which suggests that Samp1 lies upstream of SUN1 in nuclear envelope protein complexes. The hypothesis that Samp1 is part of the protein platform that regulates microtubule nucleation from the myotube nuclear envelope in concert with pericentrin and LINC components warrants future investigation. As a whole, our data identify Samp1 as a new contributor to EDMD2 pathogenesis and our data are relevant to the understanding of nuclear clustering occurring in laminopathic muscle.

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