PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Cell Nucleus”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 109 records · Page 6Linked to original sources
PubMedDate not supplied

[Photochemical transformation of Hoescht 33258 dye molecules complexed with cell nucleus DNA under the effect of UV-irradiation].

It is found that with time a decrease of fluorescence intensity of the basic band at 460 nm and appearance of a new band of fluorescence of DNA-specific dye Hoechst 33258 in complex with the cell nucleus DNA under the action of UV emission are observed. It is shown that phototransformation is related to the withdrawal of the nitrogen atom proton of piperazine ring in an excited state of the complex of the dye Hoechst 33258 with the cell nucleus DNA.

Animals↗
PubMed1975

The induction of DNA synthesis in the chick red cell nucleus in heterokaryons during the first cell cycle after fusion with HeLa cells.

Induction of DNA synthesis in embryonic chick red cells has been examined during the first and second cell cycles after fusion with HeLa cells synchronized in different parts of G1 and S-phase. The data indicate that: (i) the younger the embryonic blood the more rapidly the red cells are induced into DNA synthesis; (ii) the greater the ratio of HeLa to chick nuclei in the heterokaryon, the more rapidly the induction occurs; (iii) DNA synthesis in the chick nucleus can continue after the HeLa nucleus has left S-phase and entered either G2 or mitosis; (iv) the induction potential of late S-phase HeLa is somewhat lower than that of early or mid S-phase cells; (v) less than 10% of the chick DNA is replicated during the first cycle after fusion and only a small proportion (15%) of the chick nuclei approach the 4C value of DNA during the second cycle after fusion; (vi) the newly synthesized DNA is associated either with the condensed regions of the nucleus or with the boundaries between condensed and non-condensed regions; (vii) the chick chromosomes at the first and second mitosis after fusion are in the form of PCC prematurely condensed chromosomes); they are never fully replicated and are often fragmentary; (viii) DNA synthesis in the chick nuclei is accompanied by an influx of protein (both G1 and S-phase protein) from the HeLa component of the heterokaryon.

Amino Acids↗
PubMed1984

Myocardial cell nucleus in cardiac overloading in the rat.

The myocardial cell nucleus was studied in the rat during its normal growth and under different types of heart overloading. Under overloading of short duration, a disappearance of condensed chromatin and an increase in the nucleolus and nucleolonema were interpreted as representing cell overactivity. With isoproterenol overloading, a first stage of cell necrosis and of its consequences on chromatin and nucleolus was followed by the process of cell repair and overactivity. With overloading of long duration, several different nuclear aspects were encountered: (a) enlarged and distorted nuclei as possible supports of polyploidy; (b) a partial coupling between two adjacent nuclei, interpreted either as nuclear fusion or amitosis; (c) segregation of different proteins, probably due to cell damage. The number of nuclei per myocyte was high (90%) in the adult. It decreased (80%) two days after isoproterenol overloading, as well as in heart hypertrophy of 6-9-months duration. Nuclear size increased under isoproterenol overdosage of 48-h duration. The amount of nuclear DNA also increased two days after isoproterenol overdosage, particularly in mononucleated cells.

Animals↗
PubMed2004

Higher order chromatin architecture in the cell nucleus: on the way from structure to function.

The cell nucleus is a highly compartmentalized structure. In this review we describe controversial views on higher order chromatin organization from the level of higher order chromatin domains built up from folded chromatin fibers to the level of chromosome territories and the interchromatin compartment (IC), which harbors non-chromatin nuclear domains, such as interchromatin granule clusters (IGCs visualized in the electron microscope) or splicing factor-containing speckles (visualized by fluorescence microscopy). Emphasis is laid on the definition and functional importance of a nuclear compartment located at the periphery of chromatin domains in direct contact with the IC, termed the perichromatin region (PR). Ongoing experiments to elucidate the topological relationships between PR and IC have provided new insights into the functional interplay between transcription and splicing. As an example, we discuss the structure and nuclear topology of perichromatin fibrils (FPs) contained in the PR and their functional interplay with IGCs/speckles. In addition we discuss the advantages and drawbacks of experimental approaches currently used to study nuclear architecture and function in fixed and living cells.

Animals↗
PubMed1994

Phylogenetic analysis of 70 kD heat shock protein sequences suggests a chimeric origin for the eukaryotic cell nucleus.

BACKGROUND: The evolutionary relationships between archaebacteria, eubacteria and eukaryotic cells are of central importance in biology. The current view is that each of these three groups of organisms constitutes a monophyletic domain, and that eukaryotic cells have evolved fom an archaebacterial ancestor. Recent studies on a number of highly conserved protein sequences do not, however, support this view and raise important questions concerning the evolutionary relationships between all extant organisms, particularly regarding the origin of eukaryotic cells. RESULTS RESULTS: We have used sequences of 70 kD heat shock protein (hsp70)--the most conserved protein found to date in all species--to examine the evolutionary relationship between various species. We have obtained two new archaebacterial hsp70 sequences from the species, Thermoplasma acidophilum and Halobacterium cutirubrum. A global comparison of hsp70 sequences, including our two new sequences, shows that all known archaebacterial homologs share a number of sequence signatures with the Gram-positive group of bacteria that are not found in any other prokaryotic or eukaryotic species. In contrast, the eukaryotic homologs are shown to share a number of unique sequence features with the Gram-negative bacteria that are not present in any archaebacteria. Detailed phylogenetic analyses of hsp70 sequences strongly support a specific evolutionary relationship between archaebacteria and Gram-positive bacteria on the one hand, and Gram-negative bacteria and eukaryotes on the other. The phylogenetic analyses also indicate a polyphyletic branching of archaebacteria within the Gram-positive species. The possibility that the observed relationships are due to horizontal gene transfers can be excluded on the basis of sequence characteristics of different groups of homologs. CONCLUSIONS: Our results do not support the view that archaebacteria constitute a monophyletic domain, but instead suggest a close evolutionary linkage between archaebacteria and Gram-positive bacteria. Furthermore, in contrast to the presently accepted view, eukaryotic hsp70s show a close and specific relationship to those from Gram-negative species. To explain the phylogenies based on different gene sequences, a chimeric model for the origin of the eukaryotic cell nucleus involving fusion between an archaebacterium and a Gram-negative eubacterium is proposed. Several predictions from the chimeric model are discussed.

Amino Acid Sequence↗
PubMed1995

Nucleic acid compartmentalization within the cell nucleus by in situ transferase-immunogold techniques.

In the present review, we report on recent results obtained by in situ transferase-immunogold techniques as to the ultrastructural distribution of DNA and RNA within the cell nucleus. Special emphasis is placed on the various nucleolar components and the various enigmatic structures of the extranucleolar region: interchromatin granules, coiled bodies, and simple nuclear bodies. These data are discussed in the light of our current understanding of the functional organization of the cell nucleus.

Cell Compartmentation↗
PubMed2001

Direct exposure of chromosomes to nonactivated ovum cytoplasm is effective for bovine somatic cell nucleus reprogramming.

We examined the in vitro developmental potential of nonactivated and activated enucleated ova receiving cumulus cells at various stages of the cell cycle. Eleven to 29% of activated ova receiving donor cells stopped developing at the 8-cell stage but 21% to 50% of nonactivated ova receiving donor cells at either the G(0), G(1), G(2), or M phase, or cycling cells developed into blastocysts. One normal calf was born after transferring five blastocysts that had developed from ova receiving donor cells at the M phase. The present study demonstrated that direct exposure of donor chromosomes to nonactivated ovum cytoplasm is effective for somatic cell nucleus reprogramming, and activated ovum cytoplasm does not reprogram the nucleus.

Animals↗
PubMed1998

Cell nucleus: chromosome dynamics in nuclei of living cells.

Unraveling chromosome movements in vivo is indispensable for understanding the functional architecture of the nucleus and its relationship to the functional state of the cell. New experimental approaches have now made it possible to monitor chromosome dynamics within the nuclei of living cells.

Animals↗
PubMed1993

How does the T-DNA of Agrobacterium tumefaciens find its way into the plant cell nucleus?

Agrobacterium tumefaciens causes the crown gall disease in plants by transferring a piece of DNA, the T-DNA, into the genome of the plant cell. The virulence protein VirD2, tightly linked to the T-DNA, is thought to direct it to the plant cell nucleus and to assist it in integration. The VirD2 protein contains two nuclear localization signals (NLS) which are functional both in yeast and in plant cells. One signal is located in the N-terminal part of the protein and resembles a single-cluster type NLS. The second signal is near the C-terminus and is a bipartite type NLS. The involvement of the C-terminal NLS in the entry of the T-DNA into the plant cell nucleus was directly tested in vivo.

Agrobacterium tumefaciens↗
PubMed1978

Qualitative and quantitative odour discrimation by mitral cells as compared to anterior olfactory nucleus cells.

The responses to odour stimulation of 61 single mitral cells and of 64 single anterior olfactory nucleus (AON) units were simultaneously recorded from rabbits. The test battery consisted of 6 chemical stimuli delivered at two intensity levels corresponding to a hundred-fold difference in concentration. The odour discrimination reaches its best for the mitral cells stimulated weakly; it decreased somewhere when the same cells are stimulated strongly. At AON level the odour discrimination already limited in the case of weak stimuli, almost disappears for strong stimuli. Multidimensional analysis of the odour similarities, respectively in the olfactory bulb and the AON, reveals an unexpectedly high loading of the first axis with an intensity factor. Our results indicate that the discriminatory ability in the mitral cells and in the AON cells are respectively better and poorer than in the chemoreceptors.

Animals↗
PubMed2026

Centromeres and telomeres as rheological probes of the human cell nucleus.

The human genome contains genetic information essential for life, controlling all cellular processes via the central dogma of biology. It is a canonical example of a living polymer, yet the physical principles underlying its dynamical self-organization in the cell nucleus remain unknown. In this work, we investigate the polymeric nature of the genome in live human cells, by studying motions of the centers and free ends of linear chromosome polymers-the centromeres and telomeres-and rheology of their nuclear environment. Our findings reveal that telomeres have 10-times larger displacements than centromeres, exceeding by far predictions of polymer theories. We find that this unexpectedly large difference arises due to centromere and telomere localization in unique nuclear environments, distinct in both their biological activity and material rheology. While the former resides in the genome's silenced parts, the latter localizes in its transcriptionally active parts. Our rheological analysis shows that centromeres are embedded in an elastic environment, whereas telomeres' surroundings are viscous, directly affecting timescales and length scales of their respective motions. Our results suggest a key role of nuclear heterogeneity in genome dynamics, which we corroborate by biochemical perturbations of nuclear structures such as heterochromatin and nuclear speckles. Finally, upon homogenizing the nuclear environment by a hypoosmotic shock, we observe equal centromeric and telomeric motions, confirming our hypothesis. Our observations show that the heterogeneity of nuclear environment directly impacts timescales and length scales of local genomic motions, which may affect the spatiotemporal gene regulation across the cell nucleus.

Humans↗
PubMed1989

Dose-modification factor for accumulated dose to cell nucleus due to protein-bound 3H.

The purpose of this work was to estimate the dose-modification factor for accumulated dose in the cell nucleus due to protein-bound 3H in animal organs. The animal tissues were modeled to make a simplified theoretical estimation of the extent of dose modification due to the differential distribution of proteins between the cell nucleus and the extranuclear region. The results of theoretical calculation were applied to the case of mouse organs for which various cytological factors were determined experimentally. It was found that the dose-modifying factor (f) for mouse organs was between about 0.8 and 1.5, indicating that dose modification due to protein localization is of minor importance for the dosimetry of internally retained 3H.

Animals↗
PubMed1996

Non-isotopic electron microscope in situ hybridization for studying the functional sub-compartmentalization of the cell nucleus.

Post-embedding electron microscope in situ hybridization using gold particles as label permits the clear identification of the cellular structures which contain the nucleic acid molecules under study. It has yielded information on the distribution of defined nucleic acid sequences of different origins-cellular or viral, DNA or RNA, single- or double-stranded molecules-which has revolutionized the study of the nucleus. Application of this powerful technique in combination with other refined techniques to studies on transcription and replication of cellular and viral genes has augmented our knowledge of the functional organization of the cell nucleus. One can now ask mechanistically meaningful questions concerning the successive steps of gene replication and expression not only under normal conditions of cell growth, but also when the cellular metabolism is altered by a drug treatment or a viral infection. This chapter aims (a) to present the established methods of post-embedding electron microscope in situ hybridization for localizing, precisely and specifically, a nucleic acid target in its normal environment and (b) to present some contributions of this technique to investigations of the functional compartmentalization of the cell nucleus and to elucidate the cell-virus relationships in infected cells.

Animals↗
PubMed1997

Calcium signalling in the cell nucleus.

The First European Conference on Calcium Signalling in the Cell Nucleus took place in Baia Paraelios, Calabria, Italy, from 4-8 October 1997. It was organized by O. Bachs, E. Carafoli, P. Nicotera and L. Santella (local organizers, G. Bagetta and D. Rotiroti) and attended by about 90 specialists. The scientific content was very high and the discussions were particularly intense. Considering that the area is famous for its controversies, one could perhaps have expected aggressive overtones. Instead, in spite of the liveliness of the discussions, the atmosphere was congenial and constructive. The controversies have not disappeared, but a better understanding of some of their origins is now well under way.

Calcium↗