Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Nuclear Envelope”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,297 records · Page 72Linked to original sources
PubMed2000

Effect of cycloheximide on tryptophan binding to rat hepatic nuclei.

This study evaluated whether cycloheximide, an inhibitor of protein synthesis, would affect the binding of L-tryptophan to rat hepatic nuclei or nuclear envelopes. Previous reports have indicated that the binding of L-tryptophan to hepatic nuclear envelope protein was saturable, stereospecific, and of high affinity. Also, the administration of L-tryptophan rapidly stimulated hepatic protein synthesis. In this study, we determined that the addition of cycloheximide in vitro inhibited 3H-tryptophan binding to hepatic nuclei or nuclear envelopes. Heat-treated cycloheximide failed to have this inhibitory binding effect. In vivo treatment of rats with cycloheximide diminished in vitro 3H-tryptophan binding to hepatic nuclei of treated rats compared to controls. Puromycin, another inhibitor of hepatic protein synthesis, when added in vitro did not affect 3H-tryptophan binding to hepatic nuclei but did diminish in vitro binding after in vivo treatment. Thus, cycloheximide added in vitro diminished 3H-tryptophan binding to hepatic nuclei probably by its structural effect on the receptor while cycloheximide administered in vivo may also act in part by inhibiting protein synthesis.

Amino Acids↗
PubMed2006

Hormonal regulation of nuclear permeability.

Transport into the nucleus is critical for regulation of gene transcription and other intranuclear events. Passage of molecules into the nucleus depends in part upon their size and the presence of appropriate targeting sequences. However, little is known about the effects of hormones or their second messengers on transport across the nuclear envelope. We used localized, two-photon activation of a photoactivatable green fluorescent protein to investigate whether hormones, via their second messengers, could alter nuclear permeability. Vasopressin and other hormones that increase cytosolic Ca2+ and activate protein kinase C increased permeability across the nuclear membrane of SKHep1 liver cells in a rapid unidirectional manner. An increase in cytosolic Ca2+ was both necessary and sufficient for this process. Furthermore, localized photorelease of caged Ca2+ near the nuclear envelope resulted in a local increase in nuclear permeability. Neither activation nor inhibition of protein kinase C affected nuclear permeability. These findings provide evidence that hormones linking to certain G protein-coupled receptors increase nuclear permeability via cytosolic Ca2+. Short term regulation of nuclear permeability may provide a novel mechanism by which such hormones permit transcription factors and other regulatory molecules to enter the nucleus, thereby regulating gene transcription in target cells.

Calcium↗
PubMed2005

The KASH domain protein MSP-300 plays an essential role in nuclear anchoring during Drosophila oogenesis.

During late stages of Drosophila oogenesis, the cytoplasm of nurse cells in the egg chamber is rapidly transferred ("dumped") to oocytes, while the nurse cell nuclei are anchored by a mechanism that involves the actin cytoskeleton. The factors that mediate this interaction between nuclei and actin cytoskeleton are unknown. MSP-300 is the likely Drosophila ortholog of the mammalian Syne-1 and -2 and C. elegans ANC-1 proteins, contained both actin-binding and nuclear envelope localization domains. By using an antibody against C-terminus of MSP-300, we find that MSP-300 is distributed throughout the cytoplasm and accumulates at the nuclear envelope of nurse cells and the oocyte. A GFP fusion protein containing the C-terminal region of MSP-300 is also sufficient to localize protein on the nuclear envelope in oocytes. To eliminate the maternal gene activity during oogenesis, we generated homozygous germ-line clones of a loss-of-function mutation in msp-300 in otherwise heterozygous mothers. In the mutant egg chambers that develop from such clones, cytoplasmic dumping of nurse cells is severely disturbed. The nuclei of nurse cells and the oocyte are mislocalized and the usually well-organized actin structures are severely disrupted. These results indicate that maternal MSP-300 plays an important role in actin-dependent nuclear anchorage during cytoplasmic transport.

Actins↗
PubMedDate not supplied

[Retinol transport into the cell nucleus in vitro].

The retinol interaction with intact cellular nuclei, nuclear envelope and chromatin was investigated. We have shown that the Cellular Retinol-Binding Protein (CRBP) plays a very important role in such interaction. Retinol can specifically interacts with nuclei, nuclear envelope and chromatin only when it presents as a complex with CRBP. The obtained data allowed us to suggest that the process of retinol delivery to hypothetical nuclear receptors include of at least the following stages: 1) specific binding with nuclear envelope; 2) penetration into nuclei; 3) specific binding with chromatin receptors. CRBP is a necessary component at all this stages. Also we show that CRBP has not a species or tissue specificity.

Biological Transport↗
PubMed1974

On the attachment of the nuclear pore complex.

Electron microscope examination of isolated rat liver nuclei after treatment with the detergent Triton X-100 revealed the complete removal of both the inner and outer membranes of the nuclear envelope. The envelope-denuded nuclei did not show any change in either shape or internal ultrastructure. Most strikingly, the nuclear pore complexes, which in untreated nuclei appear to be integral components of the nuclear envelope, were retained in their characteristic location at the distal ends of the channels leading through the peripheral heterochromatin. Determination of the chemical composition of detergent-treated nuclei showed that over 95% of the nuclear phospholipid was solubilized, thus corroborating the morphological absence of nuclear membranes. Furthermore, detergent treatment also solubilized approximately 10% of the nuclear protein. Analysis of the solubilized protein by polyacrylamide gel electrophoresis in the presence of SDS indicated that these proteins belong to a few specific classes which presumably represent the major polypeptides of the nuclear membranes. The total absence of the nuclear envelope on both morphological and biochemical grounds supports the idea that the nuclear pore complex does not require the membranes either for attachment to the nucleus or for maintenance of its own structural integrity.

Animals↗
PubMed1995

Pachytene karyotype analysis of the nematode Meloidogyne spartinae in relation to the genus Meloidogyne.

Seven synaptonemal complexes (SC) were present in the pachytene nuclei of Meloidogyne spartinae. The SC was bipartite and consisted of two lateral elements, while lacking a striated central element. This pattern was similar in all Meloidogyne species studied thus far with the exception of M. microtyla. Each SC was attached by only one end to the nuclear envelope while the other end remained unattached and was free in the nucleoplasm. A bouquet formation at pachytene was absent. An average of eight recombination nodules were present on the SC during all stages of pachytene, although the length of SC increased approximately 77%, from an average of 78 to 138 microm from early to mid-late pachytene. In M. spartinae, there was no apparent relationship between SC length and amount of recombination at pachytene. In addition, nuclear volume increased >60% during pachytene while nucleolar volume decreased by approximately 35%. Two nucleolar organizer regions (NOR) were present during mid-pachytene, whereas other stages had only one NOR. This is the first time that two nucleoli have been identified at pachytene in any nematode. They were both the same chromosome yet in reverse order relative to the telomere attached to the nuclear envelope, suggesting that each telomere was competent to interact with the nuclear envelope.

Animals↗
PubMed1994

Studies with 1,1'-ethylidenebis(tryptophan), a contaminant associated with L-tryptophan implicated in the eosinophilia-myalgia syndrome.

L-Tryptophan binds to a rat liver nuclear envelope protein, and this binding is saturable, stereospecific, and of high affinity. Utilizing an in vitro assay of [3H]tryptophan binding to rat hepatic nuclear envelopes, we have previously determined that the L-tryptophan obtained from Showa Denko and which was implicated in cases of the eosinophilia-myalgia syndrome (EMS) inhibited [3H]tryptophan binding differently than did control L-tryptophan (not implicated in EMS). Therefore, in this study we investigated whether the addition of 1,1'-ethylidenebis(tryptophan) (EBT), a contaminant or impurity in L-tryptophan implicated in EMS, would have an effect. Our results indicate that EBT alone has little inhibitory binding effect compared with that of control L-tryptophan and that when EBT was added to control L-tryptophan the inhibitory binding effort was similar to that of control L-tryptophan alone. On the other hand, in vitro addition of EBT plus L-tryptophan to nuclei of cultured murine macrophages (WLG5) results in less inhibition of [3H]-tryptophan binding than does addition of L-tryptophan alone. Similar in vitro additions to nuclei of rat brain reveal little effect on binding, as was also the case for hepatic nuclear envelopes. Adding EBT to an in vitro hepatic protein synthesis system and measuring [3H]tryptophan incorporation into acid-precipitable proteins reveal that it competes similarly to that found with equimolar concentrations of unlabeled L-tryptophan. It does not affect [14C]leucine incorporation into proteins. [14C]EBT becomes incorporated in vitro into proteins (acid-precipitable), and this incorporation is diminished in the presence of equimolar concentrations of unlabeled EBT or L-tryptophan. This suggests that EBT or possibly a breakdown product becomes incorporated into proteins. Speculation as to how EBT may affect tissues in experimental animals is presented.

Animals↗
PubMed1997

Nuclear pore complex structure in birds.

The nuclear envelope consists of two parallel membranes enclosing an aqueous lumen. In places there are pores in both membranes at which the two membranes are joined. Within these pores reside the nuclear pore complexes. The current structural models of the nuclear pore complex have been derived from a number of studies using different electron microscopical techniques. Recently, using surface imaging techniques such as field emission in-lens scanning electron microscopy, novel structures have been identified, particularly at the periphery of the structure, most notably the nucleoplasmic basket. One limitation of the current models is that they are based almost entirely on nuclear envelopes isolated from amphibian oocytes and a pressing question is whether this structure is the same in other organisms and tissues. Here we have studied the structure of nuclear envelopes isolated from bird oocytes. We show that the overall structure is remarkably conserved. In particular, recently discovered peripheral structures appear very similar. We see variations in basket conformation but believe that this is related to the functional states of individual pore complexes.

Animals↗
PubMed2004

Three-dimensional ultrastructure of the ring stage of Plasmodium falciparum: evidence for export pathways.

The three-dimensional structure of the Plasmodium falciparum ring stage has been explored by reconstruction from serial sections and stereoscopic examination of tilted sections. The ring-like light microscopic appearance is related to the shape and contents of the biconcave discoidal parasite at this stage, its thick perimeter containing most of the ribosomes and its thin center containing smooth membrane organelles. The shapes of rings vary between flat and curved cuplike forms. The rough endoplasmic reticulum is a branched network continuous with the nuclear envelope. Evidence for a simple Golgi complex is seen in the presence on the outer nuclear envelope of a locus of coated vesicle budding associated with a single membranous cisterna or cluster of smooth vesicles. In middle and late stage rings this complex migrates along an extension of the nuclear envelope continuous with the rough endoplasmic reticulum. Evidence is also presented for a mechanism of exporting membrane from the parasite into the parasitophorous vacuole membrane and beyond into the red blood cell, by means of double-membraned vesicle-based exocytosis.

Animals↗
PubMed2002

Ultrastructural study on mitosis and cytokinesis in Scytosiphon lomentaria zygotes (Scytosiphonales, Phaeophyceae) by freeze-substitution.

The ultrastructure of mitosis and cytokinesis in Scytosiphon lomentaria (Lyngbye) Link zygotes was studied by freeze fixation and substitution. During mitosis, the nuclear envelope remained mostly intact. Spindle microtubules (MTs) from the centrosome passed through the gaps of the nuclear envelope and entered the nucleoplasm. In anaphase and telophase, two daughter chromosome masses were partially surrounded with endoplasmic reticulum. After telophase, the nuclear envelope was reconstructed and two daughter nuclei formed. Then, several large vacuoles occupied the space between the daughter nuclei. MTs from the centrosomes extended toward the mid-plane between two daughter nuclei, among the vacuoles. At that time, Golgi bodies near the centrosome actively produced many vesicles. Midway between the daughter nuclei, small globular vesicles and tubular cisternae accumulated. These vesicles derived from Golgi bodies were transported from the centrosome to the future division plane. Cytokinesis then proceeded by fusion of these vesicles, but not by a furrowing of the plasma membrane. After completion of the continuity with the plasma membrane, cell wall material was deposited between the plasma membranes. The tubular cisternae were still observed at the periphery of the newly formed septum. Microfilaments could not be observed by this procedure. We conclude that cytokinesis in the brown algae proceeds by fusion of Golgi vesicles and tubular cisternae, not by a furrowing of the plasma membrane.

Anaphase↗
PubMed1992

Kinetics of nucleocytoplasmic Ca2+ transients in DDT1 MF-2 smooth muscle cells.

The free calcium concentrations in the nucleus ([Ca2+]n) and in the cytoplasm ([Ca2+]c) of cultured DDT1 MF-2 smooth muscle cells were estimated using the fluorescent dye indo-1. With the use of confocal microscopy, line scans were made during the onset and the differential rise of the Ca2+ signal elicited by the agonists histamine and ATP. The results confirm our earlier findings that in these cells [Ca2+]n at rest was lower than [Ca2+]c. The present experiments show that this gradient over the nuclear envelope was also preserved in Ca(2+)-free solution containing 2 mM EGTA, underlining the selective barrier function of the nuclear envelope. During stimulation with histamine, an early Ca2+ rise in the vicinity of the nuclear envelope was found in contrast to the delayed Ca2+ rise 2 microns away on both sides of the envelope. This suggests the release of Ca2+ stored in the envelope and the perinuclear sarcoplasmic reticulum. The time course for reaching a uniform Ca2+ concentration ([Ca2+]u = [Ca2+]n = [Ca2+]c) in the nuclear and cytosolic compartment varied with the agonist used for stimulation and was dependent on the external Ca2+ concentration. The value of this uniform Ca2+ concentration itself was, however, independent of the type of stimulation. After reaching [Ca2+]u, a further rise occurred with [Ca2+]n becoming larger than [Ca2+]c. It is postulated that a critical Ca2+ concentration must be reached to induce this differential Ca2+ rise by releasing Ca2+ from an intranuclear Ca2+ store.

Adenosine Triphosphate↗
PubMed1996

Distinct egg membrane vesicles differing in binding and fusion properties contribute to sea urchin male pronuclear envelopes formed in vitro.

We have identified three distinct membrane vesicle populations from sea urchin egg cytoplasm that cooperate in assembling the male pronuclear envelope in vitro. Membranes from sea urchin egg homogenates were separated by buoyant density into five vesicle fractions, three of which bind to demembranated sperm nuclei. Each requires a membranous element (lipophilic structure) derived from the sperm nuclear envelope at the tip and base (poles) of the nucleus in order to bind. Binding is differentially sensitive to protease, high salt and N-ethyl maleimide treatment of the membrane vesicles. MV1 binds at the poles and is required for fusion of the membrane vesicle fractions to each other and to the lipophilic structures. MV2 beta binds over the entire chromatin surface and is enriched in an endoplasmic reticulum marker enzyme. MV2 alpha binds at the nuclear poles, is enriched in a Golgi enzyme marker and is required for fusion of MV2 beta. All three fractions are required for nuclear envelope formation in vitro. The results suggest a multistep process for nuclear envelope formation involving contributions from both sperm and egg, roles for both endoplasmic reticulum and non-endoplasmic reticulum-derived vesicles, and the localization of a critical element of the fusion machinery in MV1.

Animals↗
PubMed1998

HIV-1 Vpr interacts with the nuclear transport pathway to promote macrophage infection.

HIV-1 Vpr promotes nuclear entry of viral nucleic acids in nondividing macrophages and also causes a G2 cell-cycle arrest. Consistent with its role in nuclear transport, we show Vpr localizes to the nuclear envelope in both human and yeast cells. Like the importin-beta subunit of the nuclear import receptor, Vpr also interacts with the yeast importin-alpha subunit and nucleoporins. Moreover, overexpression of either Vpr or importin-beta in yeast blocks nuclear transport of mRNAs. A mutant form of Vpr (Vpr F34I) that does not localize at the nuclear envelope, or bind to importin-alpha and nucleoporins, renders HIV-1 incapable of infecting macrophages efficiently. Vpr F34I, however, still causes a G2 arrest, demonstrating that the dual functions of Vpr are genetically separable. Our data suggest Vpr functionally resembles importin-beta in nuclear import of the HIV-1 pre-integration complex and this function is essential for the role of Vpr in macrophage infection, but not G2 arrest.

Cell Nucleus↗
PubMed1962

Unusual formations of ergastoplasm in parotid acinous cells of mice.

The ergastoplasm (granular endoplasmic reticulum) of parotid acinous cells of the mouse is described with special emphasis on unusual forms of this membranous system. In the majority of the acinous cells the ergastoplasm appeared in sections to consist of a large number of separate flattened cisternae. In some acinous cells, however, the ergastoplasm was disposed as a very small number of large membranous formations. Although extensive and complicated in form, these latter formations could be seen, from the examination of a single section, to consist of a single expanse of membrane continuous with the nuclear envelope. Certain acinous cells exhibited ergastoplasmic formations which appeared to represent intermediate stages of a fragmentation or metamorphosis of the larger formations toward the more usual form of ergastoplasm. These observations suggest the possibility that the early elaboration of ergastoplasm consists in the production, in relation to the nuclear envelope, of large, complicated membranous formations that subsequently sever their connection with the nuclear envelope and form a large number of separate, or tenuously connected, cisternae. The majority of the large, complicated ergastoplasmic formations were seen in parotid glands of mice that had been starved for 4 days and subsequently fed for a variable number of hours, but some were found in glands that were not subjected to experimental treatment. The tissues studied were prepared for electron microscopic examination by fixation in osmium tetroxide, dehydration in alcohol, imbedding in butyl methacrylate, sectioning with a glass knife, staining with lead hydroxide, and sandwiching with formvar.

Acinar Cells↗
PubMed1998

Nup154, a new Drosophila gene essential for male and female gametogenesis is related to the nup155 vertebrate nucleoporin gene.

The Nup154 gene of Drosophila encodes a protein showing similarity with known nucleoporins: rat Nup155 and yeast Nup170 and Nup157. Hypomorphic mutant alleles of Nup154 affected female and male fertility, allowing investigation of the gene function in various steps of oogenesis and spermatogenesis. Nup154 was required in testes for cyst formation, control of spermatocyte proliferation and meiotic progression. In ovaries, Nup154 was essential for egg chamber development and oocyte growth. In both the male and female germ line, as well as in several other cell types, the Nup154 protein was detected at the nuclear membrane, but was also present inside the nucleus. Intranuclear localization has not previously been described for rat Nup155 or yeast Nup170 and Nup157. In mutant egg chambers the Nup154 protein accumulated in the cytoplasm, while it was only barely detected at the nuclear envelopes. FG repeats containing nucleoporins detected with mAb414 antibody were also mislocalized to a certain extent in Nup154 mutant alleles. This suggests that Nup154 could be required for localizing other nucleoporins within the nuclear pore complex, as previously demonstrated for the yeast Nup170. On the other hand, no evident defects in lamin localization were observed, indicating that Nup155 mutations did not affect the overall integrity of the nuclear envelope. However, ultrastructural analyses revealed that in mutant cells the morphology of the nuclear envelope was altered near the nuclear pore complexes. Finally, the multiplicity of phenotypes observed in Nup154 mutant alleles suggests that this gene plays a crucial role in cell physiology.

Amino Acid Sequence↗
PubMed2007

Emery-Dreifuss muscular dystrophy.

Emery-Dreifuss muscular dystrophy (EDMD) is inherited in an X-linked or autosomal manner. X-linked EDMD is caused by mutations in EMD, which encodes an integral protein of the nuclear envelope inner membrane called emerin. Autosomally inherited EDMD is caused by mutations in LMNA, which encodes A-type nuclear lamins, intermediate filament proteins associated with inner nuclear membrane. Although the causative mutations have been described and mouse models have been created, the pathogenic processes by which mutations in genes encoding nuclear envelope proteins cause striated muscle abnormalities in EDMD remain obscure. Working hypotheses include effects on nuclear structural integrity, increased cellular susceptibility to mechanical stress damage, alterations in gene expression in response to nuclear envelope changes, and effects on cell proliferation and differentiation.

History, 20th Century↗
PubMed1986

Remodelling of thymocyte nuclei in activated mouse oocytes: an ultrastructural study.

Oocyte-thymocyte mouse cell hybrids were produced using polyethylene glycol (PEG) and examined at the ultrastructural level. Fusion was accomplished either before or after activation of metaphase II oocytes. In both experimental variants thymocyte nuclei undergo remodelling which comprises the following sequence of events: nuclear envelope breakdown, initial chromatin condensation, and subsequent decondensation, nuclear envelope reformation and formation of nucleoli. In hybrids produced before oocyte activation but activated within a short time and cultured for several hours the thymocyte nuclei become identical to the female pronucleus. In the second variant (fusion with activated oocytes) the degree of remodeling of thymocyte nuclei is variable. Our observations demonstrate that between metaphase II, telophase of meiosis and early female pronuclear stages the mouse oocyte contains all "factors" necessary for remodelling of differentiated somatic nuclei and their development as if they were pronuclei.

Animals↗
PubMed1976

Arrangement of chromosome ends and axial core formation during early meiotic prophase in the male grasshopper Brachystola magna by 3D, E.M. reconstruction.

Evidence is presented that chromosome ends are attached to the nuclear envelope prior to the formation of axial cores during early meiotic prophase in the grasshopper Brachystola magna. The attachment sites of distal and proximal chromosome ends are clustered in a small region of the inner nuclear envelope resulting in a classical bouquet arrangement of the chromosomes. Proximal ends are tightly clustered due to the presence of chromocenters. Distal chromosome ends are more widely scattered throughout the base of the bouquet.--Axial core formation can be initiated at chromosome ends or at internal chromosome sites. However, there is a preference for axial cores to form in distal chromosome regions rather than proximal regions during early meiotic prophase.--Virtually all of the nuclear pore complexes are located in the general vicinity of the chromosome attachment sites but each specific attachment site is surrounded by a small area of nuclear envelope which is devoid of pore complexes.

Animals↗