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At least 19 recordsLinked to original sources
PubMed1991

Radiobiology of alpha particles. III. Cell inactivation by alpha-particle traversals of the cell nucleus.

Cell inactivation after exposure to collimated 3.5-MeV alpha particles in three hamster cell lines, V79, CHO-10B, and HS-23, one mouse cell line, C3H 10T1/2, and a human skin fibroblast cell line were studied. Several parameters were investigated for each cell line. Theoretical calculations were performed to find the distribution of energy deposited in the nuclear volume for each cell line. The mean number of alpha-particle traversals required to induce a lethal lesion varied between two for HS-23 cells and six for C3H 10T1/2 cells. The number of traversals per unit area and the total track length of alpha particles that inactivated a cell were found to be nearly constant for the hamster and mouse cell lines. These quantities were found to be lower for the human skin fibroblast cell line. The RBE values for all cell lines were found to be about 3.8 at 10% survival. Thus cell lines that are more sensitive to alpha radiation are also more sensitive to gamma radiation. The average number of alpha-particle traversals producing a single lethal lesion is greater than one. The passages of alpha particles through the cell nucleus that do not kill the cell may lead to carcinogenic effects.

Alpha Particles↗
PubMed2001

Fluorescence resonance energy transfer microscopy of localized protein interactions in the living cell nucleus.

Cells respond to environmental cues by modifying protein complexes in the nucleus to produce a change in the pattern of gene expression. In this article, we review techniques that allow us to visualize these protein interactions as they occur in living cells. The cloning of genes from marine organisms that encode fluorescent proteins provides a way to tag and monitor the intracellular behavior of expressed fusion proteins. The genetic engineering of jellyfish green fluorescent protein (GFP) and the recent cloning of a sea anemone red fluorescent protein (RFP) have provided fluorescent tags that emit light at wavelengths ranging from the blue to the red spectrum. Several of these color variants can be readily distinguished by fluorescence microscopy, allowing them to be used in combination to monitor the behavior of two or more independent proteins in the same living cell. We describe the use of this approach to examine where transcription factors are assembled in the nucleus. To demonstrate that these labeled nuclear proteins are interacting, however, requires spatial resolution that exceeds the optical limit of the light microscope. This degree of spatial resolution can be achieved with the conventional light microscope using the technique of fluorescence resonance energy transfer (FRET). The application of FRET microscopy to detect the interactions between proteins labeled with the color variants of GFP and the limitations of the FRET approach are discussed. The use of different-color fluorescent proteins in combination with FRET offers the opportunity to study the complex behavior of key regulatory proteins in their natural environment within the living cell.

Cell Nucleus↗
PubMed1988

Lipid mediated signal transduction in the cell nucleus.

Cell growth and differentiation can be affected by the transduction of extracellular signals involving cyclic nucleotides, inositol phospholipids and phospholipid dependent protein kinase C systems. Since we previously reported existence of lipids inside the nucleus and nuclear fractions, it seems of interest to examine the possible presence of the cascade of inositol lipids in isolated nuclei as well as the presence of the protein kinase C, whose activity is tightly related to the phosphoinositide cycle, and requires the presence of phosphatidylserine, which has been previously demonstrated to deeply affect nuclear structure and function. Here we show that highly purified nuclei from both rat liver and Friend cells, free of nuclear membrane, can incorporate radiolabel from ATP-[32P] into phosphatidic acid, phosphatidyl-inositol phosphate and phosphatidylinositol (4', 5')bisphosphate. The degree of radiolabelling of phosphatidylinositol bisphosphate is highly dependent on the state of differentiation of the cells. Moreover, a doublet of immunoreactive bands has been identified in rat liver nuclei by means of a polyclonal antibody against protein kinase C. The two polypeptides appear to be tightly bound to the nuclear matrix. These two forms of the enzyme might be translational products specifically located in the nucleus, involved in the transduction to the genomic apparatus of regulatory signals generated by growth factors and tumor promoters.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Coalignment of the muscle cell and nucleus, cell geometry and Vv in the tunica media of monkey cerebral arteries, by electron microscopy.

We undertook to ascertain how well aligned is the rod-shaped nucleus within the spindle-shaped cell of vascular muscle in order that we might use the darkly staining nucleus in histological sections to indicate precisely the directional alignment of the cell. We fixed cerebral arteries from five monkeys under physiological pressure and embedded portions of the tissue so that mid-plane longitudinal sections of the arteries were obtained; the circumferentially arranged muscle cells were cut in cross-section. From the electron micrographs we obtained the cross-sectional profile of the cell and its nucleus, determining that the centre of the nucleus was on average 9.5 +/- 5.8% (SD) away from the centre of the cell (expressed as a ratio of the cellular diameter). We calculated the alignment between the cell and nucleus to be from 0 to 3 degrees, and obtained a volume fraction of 59% for muscle tissue in the tunica media of these arteries.

Animals↗
PubMed2000

EMBO workshop report. An eclipse over the cell nucleus functional organization of the cell nucleus Prague, August 9-12, 1999.

The EMBO workshop 'Functional Organization of the Cell Nucleus' held in Prague at the Hotel of the Postgraduate School of Medicine was attended by 110 participants (49 invited speakers and 61 selected participants) from 22 countries. Such a full range of topics devoted to the cell biology of the nucleus has not been discussed previously in such an intimate meeting in Europe. The workshop not only offered an opportunity for junior scientists to benefit from having an international meeting within Europe and a chance to discuss their work with internationally recognized experts, but it also offered a unique opportunity for interactions among the more established investigators. The fruits of a number of presentations are gathered together in a Special Issue of the Journal of Structural Biology which appeared in spring 2000. Last but not least, it is worth mentioning that while stepping through a packed scientific program, the participants did find the time to observe the solar eclipse just before the lunch break of August 11.

Apoptosis↗
PubMedDate not supplied

Compartmentalization of regulatory proteins in the cell nucleus.

The cell nucleus is increasingly recognized as a spatially organized structure. In this review, the nature and controversies associated with nuclear compartmentalization are discussed. The relationship between nuclear structure and organization of proteins involved in the regulation of RNA polymerase II-transcribed genes is then discussed. Finally, very recent data on the mobility of these proteins within the cell nucleus is considered and their implications for regulation through compartmentalization of proteins and genomic DNA are discussed.

Acetylation↗
PubMed1991

A histometrical and comparative study on Purkinje cell loss and olivary nucleus cell loss in multiple system atrophy.

We examined pathologically 21 cases of multiple system atrophy (MSA). Density of Purkinje cell in 16 cases and of olivary nucleus cell in 20 cases was quantitatively measured, and their distribution as well as degree were studied. Contrary to the findings of previous reports, Purkinje cell loss was more pronounced in the vermis than in the hemispheres. Olivary nucleus cell loss was more outstanding in the accessory nucleus than in the inferior nucleus. A topographical characteristic of cell degeneration exists between the Purkinje layer and the olivary nucleus. Significant sparing of the nodulus apparently related to that of the vestibular system was found. While the common distribution of cell loss was seen, its degree varied considerably case by case. The degree was related to both duration of illness and, to some extent, clinical subtypes of MSA.

Atrophy↗
PubMed2004

Circadian tracking of nicotinamide cofactor levels in an immortalized suprachiasmatic nucleus cell line.

Nicotinamide adenine dinucleotides can exhibit a daily rhythm in plants and regulate the activity of mammalian clock-like transcription factors in vitro. Because one such redox-sensitive transcription factor is present in the master circadian clock of the brain (the suprachiasmatic nuclei, SCN) and the SCN exhibits a characteristic daily rhythm in glucose usage, nicotinamide cofactors might be expected to influence, exhibit, and/or reflect biological rhythms in SCN cells. Therefore, cofactors were extracted from a model SCN cell line at 3 h intervals over 1-2 day periods and samples were analyzed by capillary electrophoresis with multiphoton excitation of fluorescence. Natively fluorescent reduced cofactors (nicotinamide adenine dinucleotide, NADH, and its phosphorylated form, NADPH) were assayed directly, and nonfluorescent oxidized cofactors (nicotinamide adenine dinucleotide, NAD, and its phosphorylated form, NADP) were enzymatically reduced to their fluorescent counterparts before analysis. In the first day after a synchronizing pulse of fetal bovine serum, a dramatic upregulation in cellular NADH content was observed, consistent with a response to serum insulin; this was accompanied by a smaller decrease in NADPH redox state, which may indicate scavenging of reactive oxygen species generated by increased cellular metabolism. However, when cells were investigated after these early phenomena had recovered or stabilized, no circadian NAD(P)(H) rhythms were observed. During these studies, the NADH/NAD(H) concentration ratio in SCN2.2 cells (0.13+/-0.03) was not high enough to activate clock-like transcription factors. Although the NADPH/NADP(H) concentration ratio was more appropriate (0.8+/-0.1), the intracellular NADPH concentration was < or = 0.7 mM, far too low for half-maximal DNA binding of clock-like transcription factors in vitro. Moreover, these concentration and ratio values represent cellular averages, and free cofactors should be much lower in the cell nucleus. Our data show that SCN2.2 cells maintain nearly constant circadian NAD(P)(H) levels, and that the previously reported in vitro relationship between clock-like transcription factors and NAD(P)(H) does not appear to be biologically relevant.

Animals↗
PubMed2000

Radiation doses to the cell nucleus in single cells and cells in micrometastases in targeted therapy with (131)I labeled ligands or antibodies.

PURPOSE: The aim of this study was to theoretically investigate how the radiation dose to cell nuclei depends on the subcellular position of (131)I. The influence of the size of the cells and crossfire irradiation in clusters of cells was also studied. METHODS AND MATERIAL: Using data describing the dose rate around a point source of (131)I, we calculated the dose distributions inside and around cell models of different sizes. The assumed positions of (131)I were on the cellular or nuclear membrane, in the cytoplasm, in the nucleus, or spread in the whole cell. The mean doses to the nucleus of the targeted cell and to the nuclei of its neighbors were calculated using the dose distributions. RESULTS: The dose distributions inside a single targeted cell showed very different distribution profiles depending on the subcellular position of the (131)I. Targeting the nucleus instead of the cellular membrane could increase the dose to the nucleus 10-fold. Crossfire irradiation can be the major contributor to the nuclear dose in clusters of more than six cells. CONCLUSIONS: Dosimetry without microscopic considerations is inadequate for targeted radionuclide therapy of disseminated or clustering tumor cells exposed to (131)I. Therapeutic doses could be achieved, even in single cells, when (131)I was positioned near, or inside the cell nucleus, or when the clusters were large enough.

Cell Count↗
PubMed1995

Localization of the glucocorticoid receptor in discrete clusters in the cell nucleus.

The cell nucleus is highly organized. Many nuclear functions are localized in discrete domains, suggesting that compartmentalization is an important aspect of the regulation and coordination of nuclear functions. We investigated the subnuclear distribution of the glucocorticoid receptor, a hormone-dependent transcription factor. By immunofluorescent labeling and confocal microscopy we found that after stimulation with the agonist dexamethasone the glucocorticoid receptor is concentrated in 1,000-2,000 clusters in the nucleoplasm. This distribution was observed in several cell types and with three different antibodies against the glucocorticoid receptor. A similar subnuclear distribution of glucocorticoid receptors was found after treatment of cells with the antagonist RU486, suggesting that the association of the glucocorticoid receptor in clusters does not require transformation of the receptor to a state that is able to activate transcription. By dual labeling we found that most dexamethasone-induced receptor clusters do not colocalize with sites of pre-mRNA synthesis. We also show that RNA polymerase II is localized in a large number of clusters in the nucleus. Glucocorticoid receptor clusters did not significantly colocalize with these RNA polymerase II clusters or with domains containing the splicing factor SC-35. Taken together, these results suggest that most clustered glucocorticoid receptor molecules are not directly involved in activation of transcription.

Animals↗
PubMed1985

Rotation of the cell nucleus in living cells: a quantitative analysis.

Nuclear rotation is observed in a variety of cell types. However, few quantitative analyses are reported and the significance of this phenomenon is still unclear. To investigate this type of nuclear movement, we performed a quantitative analysis in mouse L-929 fibroblasts, a cell line chosen since it displays a high nuclear rotational activity. Analyses were performed using time-lapse microcinematography. The relationship between nuclear rotation and other cellular phenomena such as the cell cycle and locomotion were studied. Then, we investigated the rotation in a population of sister cells to study whether it is genetically determined. Finally, we performed a qualitative analysis of nuclear rotation in different cultured cell lines. Results show that nuclear rotations preferentially occur during the phases of the cell cycle which surround mitosis.

Animals↗
PubMed1989

[The role of the muscle cell nucleus in the mechanism of its transformation after infection by Trichinella spiralis larvae. II. Histochemical features of the functional transformation of the muscle cell nucleus in the course of infection].

The activation of muscle cell nucleus in the course of T. spiralis infection, established using morphological methods (part I), has been confirmed in histochemical (histones, RNP) and histoenzymatic (RN-aze) investigations. The activity of the cell nucleus increased from the 5th day after infection up to the complete encapsulation of the larva (30th day) however it remained at a weak stable level in later stages of infection.

Animals↗
PubMed1991

Postmitotic reassembly of the cell nucleus in whole cells: an electron-spectroscopic study.

By electron-spectroscopic imaging it is possible to visualize selectively the distribution of phosphorus-rich structures such as nucleosomes, ribosomes or other ribonucleoprotein particles. Using this method we re-examined assembly of the nucleus in telophase of dividing onion root cells and human HeLa cells. Our observations disagree considerably with conclusions drawn from work with cell-free systems. We consistently observed reassembly of nuclear envelope cisternae from vesicles in the cytoplasm without direct contact with chromatin. The preassembled envelope cisternae then enclosed the telophase chromosome mass, contacting the chromatin in some tracts, but also trapping cytoplasmic material such as ribosomes between chromosomes and envelope. Until a late stage in telophase the re-forming nuclear envelope left large gaps between the nuclear and the cytoplasmic compartments. Exclusion of cytoplasmic material from the re-assembling nucleus was facilitated by prenucleolar material, which accumulated in the deep furrows of the chromosomes and interchromosomal spaces. This material expanded considerably while the envelope was still open, in this way displacing cytoplasm non-selectively from the future nucleus. The model we propose for reassembly of the nucleus in whole cells does not postulate contact with and complete enclosure of chromosomes by the re-forming envelope, and suggests a decisive role for expanding prenucleolar material in the process of nucleocytoplasmic compartmentalization.

Cell Nucleolus↗