PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Cell Nucleus Structures”

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 289 records · Page 16Linked to original sources
PubMed2007

Polyalanine expansion mutations in the X-linked hypopituitarism gene SOX3 result in aggresome formation and impaired transactivation.

Polyalanine expansion mutations have been identified in eight transcription factors that are associated with a range of congenital disorders. While some of these mutant proteins have been shown to generate cellular aggregates in heterologous cell lines, little is known about the mechanism by which these aggregates cause disease. Here we examine the aggregation and functional properties of the two known polyalanine expansion mutations associated with X-linked Hypopituitarism (XH), SOX3(22Ala) and SOX3(26Ala), which contain an additional seven and eleven alanine residues, respectively. SOX3(22Ala) and SOX3(26Ala) proteins form cytoplasmic aggregates and nuclear inclusions in transiently transfected COS-7 and CHO K1 cells, and in transfected explant cultures of chick neural epithelium. SOX3(26Ala) exhibits a more potent aggregation phenotype, resulting in significantly more cells with dispersed cytoplasmic and large perinuclear aggregates. SOX3(22Ala) and SOX3(26Ala) protein aggregates exhibit the key properties of aggresomes including vimentin redistribution, colocalisation with the Microtubule Organising Centre and sensitivity to microtubule disruption. This is the first time that aggresomes have been implicated in the aetiology of a polyalanine expansion disorder, suggesting that XH and protein conformation disorders may become manifest through similar pathological mechanisms. Further, we show that mutant SOX3 proteins have impaired transcriptional activity and reduced capacity to inhibit beta-catenin/TCF-mediated transcription. These data suggest that deregulation of SOX3 target genes and inappropriate canonical Wnt signaling in central nervous system (CNS) progenitors may also contribute to dysfunction of the hypothalamic-pituitary axis in XH patients.

Animals↗
PubMed2002

rDNA amplification in previtellogenic and vitellogenic oocytes of symphylans (Arthropoda, Myriapoda).

Tube-shaped ovaries of symphylans house numerous developing oocytes that are accompanied by somatic follicular cells. Oocyte nuclei (germinal vesicles) are relatively large and ovoid. During early previtellogenesis they contain compact spherical bodies and lampbrush chromosomes immersed in a translucent karyoplasm. Fluorescent labeling with DAPI and propidium iodide has revealed the presence of both DNA and RNA in the spherical bodies. As previtellogenesis advances, small RNA- and AgNOR-positive nucleoli bud off from these bodies. Full-grown nucleoli consist of coarse-granular material and comprise electron-transparent vacuoles. Our results suggest that in symphylan germinal vesicles amplification of rDNA genes takes place, and that the spherical bodies represent accumulations of extrachromosomal rDNA (rDNA bodies) after commencement of transcriptional activity.

Animals↗
PubMed2002

Intranuclear virus-like particles of a Drosophila hybrid.

Intranuclear virus-like particles (VLPs) have been observed in different cell lines and adult tissues of Drosophila. In the present study, intranuclear VLPs have been found in larval tissues (salivary glands, midgut, fat body) as well as in adult tissues (midgut, genitals, fat body) of a rare interspecific hybrid (D. mauritiana x D. melanogaster) called 'mame'. The intranuclear VLPs were round or slightly elliptical with a diameter of 30 nm, and they were found mainly in highly organised clusters, forming large crystalline arrays, near the nucleolus and the polycene chromosomes. These particles were never observed in the cytoplasm of any mame's tissue. A few VLPs were also seen in the corresponding tissues of D. melanogaster, but they were never observed in any tissue of D. mauritiana. There is the intriguing possibility that these VLPs are related to transposable elements and probably contribute to the speciation process, in an unknown, so far, manner.

Animals↗
PubMed1998

Communication between the cell membrane and the nucleus: role of protein compartmentalization.

Understanding how the information is conveyed from outside to inside the cell is a critical challenge for all biologists involved in signal transduction. The flow of information initiated by cell-cell and cell-extracellular matrix contacts is mediated by the formation of adhesion complexes involving multiple proteins. Inside adhesion complexes, connective membrane skeleton (CMS) proteins are signal transducers that bind to adhesion molecules, organize the cytoskeleton, and initiate biochemical cascades. Adhesion complex-mediated signal transduction ultimately directs the formation of supramolecular structures in the cell nucleus, as illustrated by the establishment of multi complexes of DNA-bound transcription factors, and the redistribution of nuclear structural proteins to form nuclear subdomains. Recently, several CMS proteins have been observed to travel to the cell nucleus, suggesting a distinctive role for these proteins in signal transduction. This review focuses on the nuclear translocation of structural signal transducers of the membrane skeleton and also extends our analysis to possible translocation of resident nuclear proteins to the membrane skeleton. This leads us to envision the communication between spatially distant cellular compartments (i.e., membrane skeleton and cell nucleus) as a bidirectional flow of information (a dynamic reciprocity) based on subtle multilevel structural and biochemical equilibria. At one level, it is mediated by the interaction between structural signal transducers and their binding partners, at another level it may be mediated by the balance and integration of signal transducers in different cellular compartments.

Animals↗
PubMed1983

The influence of GABAergic inhibitory processes on the receptive field structure of X and Y cells in cat dorsal lateral geniculate nucleus (dLGN).

Visually elicited inhibitory processes, underlying the receptive field structure of cells in layers A and A1 of the cat dorsal lateral geniculate nucleus (dLGN), have been examined by a combination of visual neurophysiological and iontophoretic techniques. Discrete visual stimulation of both centre and surround mechanisms, produced a powerful suppression of the elevated background discharge levels induced by iontophoretic application of an excitatory amino acid. These observations are consistent with the activation of a postsynaptic inhibitory input, a view supported by the fact that the suppressive effects were blocked by iontophoretic application of bicuculline, an antagonist of GABA, a putative inhibitory transmitter in the dLGN. These inhibitory effects were always elicited by the opposite phase of a flashed stimulus to that eliciting responses associated with the receptive field region. That is 'on' inhibitory effects were elicited from 'off' excitatory regions and 'off' inhibitory effects from 'on' excitatory regions. Plotting the responses of dLGN cells to flashed stimuli of increasing diameter, before and during iontophoretic application of bicuculline, revealed a marked reduction of the surround antagonism of centre response in the presence of the drug. During bicuculline application, surround antagonism of centre responses was at a level associated with that seen in retinal ganglion cells. Annular stimuli of internal and external diameter selected to be just outside the centre-surround border, insofar as they gave pure surround responses, were observed in the presence of bicuculline to elicit strong centre responses, as well as surround responses. These observations indicate that GABAergic inhibitory processes generate the enhanced centre-surround antagonism associated with dLGN cells and serve to increase the contrast between the two sets of mechanisms at the centre-surround border. The present conclusions apply equally to 'X' and 'Y' cells.

Animals↗
PubMed2002

A protein encoded by the herpes simplex virus (HSV) type 1 2-kilobase latency-associated transcript is phosphorylated, localized to the nucleus, and overcomes the repression of expression from exogenous promoters when inserted into the quiescent HSV genome.

Herpes simplex virus (HSV) is characterized by its ability to establish a latent infection in sensory neurons, from which it can periodically reactivate. The mechanisms of latency, however, remain unclear. The HSV genome is quiescent during latency except for the expression of the latency-associated transcripts (LATs). Although the exact function of the LATs remains obscure, current evidence suggests they are multifunctional and are involved in both establishment of latency and reactivation from latency. The LATs contain several open reading frames (ORFs). One or more of the functions of the LATs could therefore be protein mediated. We have previously reported that deregulated expression of the largest of the HSV type 1 (HSV-1) LAT ORFs ( approximately 274 amino acids) greatly enhances virus growth in cell types that are normally relatively nonpermissive for HSV replication and also that it complements mutations to the immediate-early (IE) gene ICP0 (S. K. Thomas, G. Gough, D. S. Latchman, and R. S. Coffin, J. Virol. 73:6618-6625, 1999). Here we show that LAT ORF expression overcomes the repression of expression from exogenous promoters introduced into the HSV-1 genome which normally occurs in the absence of IE gene expression. To further explore LAT ORF function, we have generated an epitope-tagged LAT ORF, LATmycHis, which forms punctate structures in the infected-cell nucleus reminiscent of the structures formed by ICP0. These are associated with the appearance of a phosphorylated form of the protein and are formed adjacent to, or around the edges of, viral replication compartments. These results provide further evidence that the HSV-1 LAT ORF protein is biologically functional and that the tightly regulated expression of this protein may be important in the wild-type latency phenotype in vivo.

Animals↗