Synthesis of proteins in cells infected with herpesvirus. VII. Lack of migration of structural viral proteins to the nucleus of arginine-deprived cells.
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Animals↗
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Results for “Cell Nucleus Structures”
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[Participation of microfilaments in the formation of adhesion plaques and their importance in cell shape and proliferative regulation].
Cell adhesion to an extracellular matrix or other suitable substrata is correlated with the formation of adhesion plaques and the bundling of microfilaments. A model of the structure of the adhesion plaque is given, considering some recent data on proteins which are involved: adhesion proteins (collagen, fibronectin, laminin etc.), receptors of adhesion proteins (e.g. integrin), components of the membrane skeleton (talin, vinculin etc.), and cytoskeletal proteins. Furthermore, the structure of microfilaments, their interaction with the membrane skeleton and other elements of the cytoskeleton as well as their role in cell flattening are discussed. Several results from literature are presented which hint at the significance of the cytoskeleton in growth regulation. From experiments on growth regulation of lens epithelial cells the following conclusion were drawn: Cell substratum contact is a precondition for the organization of microfilaments. Intact microfilaments and a rigid substratum are necessary for the development of isometric traction forces. Traction forces produced by the microfilaments alter the shape and structure of the cell nucleus and may be involved in inducing a replication competent chromatin structure.
Actin Cytoskeleton↗
On the role of the nucleus in the structural organization of the cell: dispersion and rearrangement of the Golgi complex in cytoplasts treated with antimicrotubular drugs.
Using cytochemical and electron microscopic techniques, it was shown that enucleated L929 fibroblasts retained a radiating pattern of microtubules as well as a large and circumscribed Golgi complex for at least one day. At the same time, the number of ribosomes and the overall size of the rough endoplasmic reticulum were reduced, probably as a result of the arrest in production of new mRNA. Treatment of the cytoplasts with either of the microtubule-disruptive drugs colchicine or nocodazole led to loss of microtubules, aggregation of intermediate filaments in large bundles, and a characteristic disorganization of the Golgi complex with spreading of its constituent stacks of cisternae throughout the cytoplasm. After withdrawal of the drugs, microtubules reappeared, intermediate filament bundles disaggregated, and the Golgi complex resumed a morphology comparable to that of cells kept in normal medium during the entire experiment. In all these respects, the cytoplasts behaved in a similar way as nucleated cells. The observations confirm earlier notions of a role of the microtubular cytoskeleton in the organization of the Golgi complex. They further indicate that the information needed to support the normal structure and interaction of these organelle systems is present in the cytoplasm and does not require the physical presence of the nucleus, nor continuous nuclear activity, i.e. transcription and processing of mRNA.
Animals↗
[Organizing the sperm nucleus].
Thanks to the success of new assisted reproductive technology, including sperm microinjection (i.c.s.i.), men with severe spermatogenesis impairments can now become biological fathers. Whether the germinal cell used for i.c.s.i. is conveying appropriate genetic and epigenetic information is an important concern. However, to date, there is a huge lack of data on which information is epigenetically conveyed to the offspring and how. The basic support for epigenetic marks is the nucleus structure. During spermatogenesis, a major re-organization of the male germ cells nucleus structure occurs, which includes a global condensation associated with a removal of most core somatic histones and their replacement by sperm-specific nuclear proteins. The available data on the molecular mechanisms involved in this process and how it could relate to the setting of male-specific epigenetic information is reviewed and discussed in light of our current knowledge about nuclear structure and functions.
Cell Nucleus↗
Structural and functional classes of multipolar cells in the ventral cochlear nucleus.
Multipolar cells in the ventral cochlear nucleus (VCN) are a structurally and functionally diverse group of projection neurons. Understanding their role in the ascending pathway involves partitioning multipolar cells into distinct populations and determining where in the brain each sends its coded messages. In this study, we used retrograde labeling techniques in rats to identify multipolar neurons that project their axons to the ipsilateral dorsal cochlear nucleus (DCN), the contralateral CN, or both structures. Three rats received injections of biotinylated dextran amine in the ipsilateral DCN and diamidino yellow in the contralateral CN. Several radiate multipolar neurons (defined by their axonal projections to the ipsilateral DCN and their dendrites that traverse VCN isofrequency sheets) were double-labeled but over 70% were not. This result suggests two distinct populations: (1) radiate-commissural (RC) multipolar cells that project to the ipsilateral DCN and the contralateral CN, and (2) radiate multipolar cells that project exclusively (in this context) to the ipsilateral DCN. In a different group of animals, we retrogradely labeled multipolar neurons that project their axons to the contralateral CN and measured the size of their cell bodies. The mean size of this population (266 +/- 156 microm2) was significantly smaller than those of RC-multipolar cells (418 +/- 140 microm2). We conclude that the CN commissural pathway is composed of at least two components: (1) RC multipolar cells and (2) commissural multipolar cells that are small- and medium-sized neurons that project exclusively (in this context) to the contralateral CN. These results identify separate structural groups of multipolar cells that may correspond to physiological unit types described in the literature. They also provide protocols for isolating and studying different populations of multipolar cells to determine the neural mechanisms that govern their responses to sound.
Amidines↗
[Revised version of the of the concept of digesting mental information].
The concept of information metabolism was introduced by prof. Kepiński at the end of the 1960-ies of the 20th century. The article presents the synthesis of a series of papers aiming to concrete, update and describe in mathematical terms the concept of metabolism of information. Theoretical basis of the model in the context of the theory of information and the main structures and functions of the metabolism of information are presented. These structures are: control centre (nucleus), boundaries (cell membrane), functional structures (endoplasmic reticulum), energy centres (mitochondria), synthesis centres (ribosoms) and elimination centres (lysosoms). At the end, the publications on the mathematical description of the information metabolism model are presented and discussed.
Brain↗
A physiological and structural study of neuron types in the cochlear nucleus. II. Neuron types and their structural correlation with response properties.
The present study examined the morphological cell types of neurons labeled with intracellular horseradish peroxidase injections, many of them following electrophysiological recordings in the cochlear nucleus of gerbils and chinchillas. Most of the subdivisions and neuronal types previously described in the cat were identified in the present material, including spherical and globular bushy cells, stellate, bushy multipolar, elongate, octopus, and giant cells in the ventral cochlear nucleus, and a cartwheel cell in the dorsal cochlear nucleus. In many cases these structurally distinct neurons were correlated with their characteristic responses to stimulation by sound or intracellular injection of depolarizing current. The dendritic terminals of the elongate, antenniform, and clavate cells of the posteroventral cochlear nucleus link each of these cell types with neighboring structures in distinct patterns, which may provide a basis for differences in synaptic organization. These cell types differ from each other and from the stellate cells of the anteroventral cochlear nucleus. Despite their heterogeneous morphology, most of these neurons had a regular discharge in response to stimulation (choppers). Irregularly firing neurons (primary-like) had very different structures, e.g., the spherical and globular bushy cells and the bushy multipolar neuron. They, too, represent a heterogeneous population. An onset neuron was identified as an octopus cell. This paper compares the morphological observations with the electrophysiological properties of different cell types reported in a companion paper (Feng et al. [1994] J. Comp. Neurol.). Together, these findings imply that response properties may be partially independent of neuronal structure. Morphologically distinct neurons can generate similar temporal patterns in response to simple acoustic stimuli. Nevertheless, the synaptic organization of these different neuron types, including their connections, would be expected to affect or alter the cells' responses to appropriate stimuli. The possibility is raised that membrane properties and synaptic organization complement and interact with each other.
Animals↗
Adenovirus infection targets the cellular protein kinase CK2 and RNA-activated protein kinase (PKR) into viral inclusions of the cell nucleus.
The effects of the adenovirus infection on the distribution of the cellular protein kinase CK2 and double-stranded RNA-activated protein kinase (PKR) were examined at the ultrastructural level. Immunogold labeling revealed the redistribution of CK2 subunits and PKR to morphologically distinct structures of the cell nucleus. The electron-clear amorphous structures, designated pIX nuclear bodies in our previous work (Rosa-Calatrava et al., 2001), contained CK2 alpha and PKR. The protein crystals, which result from the regular assembly of hexon, penton base, and fiber proteins [Boulanger et al. (1970) J Gen Virol 6:329-332], contained CK2 beta and PKR. Both viral structures were devoid of viral RNA, including the PKR-inhibitor VA1 RNA generated by the RNA polymerase III. Instead, VA1 RNA accumulated in PKR-free viral compact rings in which the viral RNA generated by the RNA polymerase II was excluded.
Adenoviruses, Human↗
Differences in function and structure of the capillary endothelium in the supraoptic nucleus and pituitary neural lobe of rats. Evidence for the supraoptic nucleus as an osmometer.
The physiology and structure of capillary endothelial cells in the hypothalamic ventromedial and supraoptic nuclei and pituitary neural lobe were evaluated with quantitative methods and compared. The capillary endothelial cells in the ventromedial nucleus were used as an index of blood-brain barrier endothelium in cerebral gray matter; this endothelium has relatively low surface area and low permeability to tracer solutes. The permeability X surface area product of endothelial cells for a neutral amino acid, 14C-alpha-aminoisobutyric acid (AIB), in the ventromedial nucleus was similar to the value for supraoptic nucleus and was several hundred times smaller than in the neural lobe. The supraoptic nuclei and neural lobe had exceptionally large capillary surface areas, but dissimilar rates of blood flow and transendothelial influx of AIB. Differences in permeability of the endothelial cells between these two structures correlated closely with their marked dissimilarities in morphology. The neural lobe endothelium had numerous fenestrations (five per capillary cross-section) and vesicular profiles (twice as many as supraoptic nucleus), two features commonly associated with high capillary permeability. The capillary endothelium of the supraoptic nucleus was that of a typical blood-brain barrier structure having intercellular junctions that appeared tight, no fenestrations, and few cytoplasmic pits and vesicles. The unusually large capillary surface area of the supraoptic nucleus and low rate of solute flux across its endothelial cells make this nucleus a unique structure in which rapid changes in tissue volume may occur in response to small perturbations in plasma osmolality. The findings implicate the supraoptic nucleus as an osmotically sensitive detector or 'osmometer' in neuroendocrine regulation of body fluid homeostasis.
Animals↗
Chromatin structure exhibits spatio-temporal heterogeneity within the cell nucleus.
Local chromatin compaction undergoes dynamic perturbations to regulate genetic processes. To address this, the direct measurement of the fluidity of chromatin structure is carried out in single live cells using steady-state anisotropy imaging and polarization modulation microscopy. Fluorescently tagged core and linker histones are used to probe different structural aspects of chromatin compaction. A graded spatial heterogeneity in compaction is observed for the chromatin besides the distinct positional ordering of core and linker histones. These spatio-temporal features are maintained by active processes and perturbed during death. With cell cycle, the distribution in compaction heterogeneity continually changes maximizing during M-G1 transition where it displays bimodal behavior. Such measurements of spatio-temporal chromatin fluidity could have broader implications in understanding chromatin remodeling within living cells.
Adenosine Triphosphate↗
Monoclonal antibodies specific for tight-binding human chromatin antigens reveal structural rearrangements within the nucleus during the cell cycle.
The class of nonhistone chromosomal proteins that remains bound to DNA in chromatin in the presence of 2.5 M NaCl-5 M urea has proven refractile to biochemical analysis. In order to study its role in chromatin organization, we have produced monoclonal antibodies that are specific for the HeLa DNA-protein complex that remains after extraction of chromatin with high salt and urea. The antibody-producing clones were identified with an ELISA assay. Of the six clones selected, five were stabilized by limiting dilution. All clones are IgG producers. None cross-react significantly with native DNA, core histones, or the high-mobility group nonhistone proteins. All antibodies are specific for nuclear or juxtanuclear antigens. Indirect immunofluorescence shows that three antibodies, which are nonidentical, stain three different nuclear networks. Available evidence indicates that two of these networks are the nuclear matrix. A fourth antibody reveals structures reminiscent of chromocenters. A fifth antibody, AhNA-1, binds to interphase HeLa chromatin and specifically decorates metaphase chromosomes. AhNA-1 similarly recognizes rat chromosomes. Each of these monoclonal antibodies also reveals a changing pattern of nuclear staining as cells progress through the cell cycle. Presumably, this reflects the rearrangement of the cognate antigens.
Animals↗
[Ultrastructural changes in the nucleus and the nucleolus of Euglena gracilis Z during the cell cycle].
The chromosomes and nucleolus of the Euglenineae remain visible in electron microscopy throughout the cell cycle. This peculiarity allowed to show cyclic variations of the nucleus structure in synchronized cells of Euglena gracilis Z: I. different stages of chromosome condensation was observed; 2. ultrastructural modifications in the organization of the nucleolus were evidenced, characterized by its apparent continuity ("open appearence") or discontinuity ("closed appearance") with the nucleoplasm.
Cell Division↗
[Chemically-induced mobilization of chromatin from plant cell nuclei].
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Cell Nucleus↗
Chromatin patterns in Spirillum anulus.
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Cell Nucleus↗
[Chromatin associated with the nucleolus of various mammals].
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Animals↗
The paradoxical nature of DNA damage and cell death induced by 125I decay.
Chinese hamster ovary cells were synchronized at the G1/S-phase boundary of the cell cycle and pulse-labeled for 10 min with 125I-iododeoxyuridine 30 min after entering the S phase. Cell samples were harvested for freezing and 125I-decay accumulation at intervals ranging from 15 to 480 min after termination of labeling. The survival data showed a marked shift from cell killing characteristic of low-LET radiation to that more characteristic of killing by high-LET radiation with increasing intervals between DNA pulse-labeling and decay accumulation. Cells harvested and frozen within 1 h after pulse-labeling yielded a low-LET radiation survival response with a pronounced shoulder and a large D0 of up to 0.9 Gy. With longer chase periods the shoulder and the D0 decreased progressively, and cells harvested 5 h after pulse-labeling or later exhibited a high-LET survival response (D0: 0.13 Gy). Two interpretations for these findings are discussed. (1) If DNA is the sole target for radiation death, the results indicate that DNA maturation increases radiation damage to DNA or reduces damage repair. (2) If radiation cell death involves damage to higher-order structures in the cell nucleus, the findings suggest that newly replicated DNA is not attached to these structures during the initial low-LET period, but 125I starts to induce high-LET radiation effects as labeled DNA segments become associated with the target structure(s). On balance, or data favor the latter interpretation.
Animals↗
Investigation of a test system for the rapid differentiation of nuclear and cytoplasmic damage in eucaryotes.
The effect of various agents which cause cell inactivation on the growth curves and RNA synthesis rates of yeast cells has been studied. On the basis of these investigations it was concluded that such studies can be used as a rapid test system for drawing preliminary conclusions as to whether a particular agent primarily damages the DNA of the cell nucleus or cytoplasmic structures.
Acrylonitrile↗