Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cytoplasmic Structures”

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 325 records · Page 18Linked to original sources
PubMed1996

The vesiculo-vacuolar organelle (VVO): a distinct endothelial cell structure that provides a transcellular pathway for macromolecular extravasation.

The vesiculo-vacuolar organelle (VVO) is a recently described organelle found in the cytoplasm of endothelial cells that line tumor microvessels and normal venules. VVOs are grape-like clusters of interconnecting uncoated vesicles and vacuoles, bounded by trilaminar unit membranes, that span the entire thickness of vascular endothelium, thereby providing a potential trans-endothelial connection between the vascular lumen and the extravascular space. Macromolecular tracers preferentially cross hyperpermeable tumor microvessels through VVOs. The present investigation was undertaken to elucidate further the ultrastructure and function of VVOs in a murine ovarian carcinoma (MOT) and in normal venules. Morphometry revealed that VVOs were enormous cytoplasmic structures (median area, 0.12-0.14 microns2 in single electron micrographs). Moreover, the individual vesicles and vacuoles that comprised VVOs were on average substantially larger than capillary caveolae and followed a non-normal distribution that was skewed to the right. Specimen tilting provided conclusive evidence that individual VVO vesicles and vacuoles communicated with each other and with the endothelial cells' plasma membranes by stomata, some of which were closed by diaphragms composed of a single membrane. Studies with two tracers, ferritin (FE, diameter approximately 11 nm) and horseradish peroxidase (HRP, diameter approximately 5 nm), revealed that passage of macromolecules through VVOs was regulated at the level of stomatal diaphragms, thereby demonstrating a mechanism for controlling the passage of macromolecules across endothelial cells. Thus, compared with tumor microvessels, little circulating FE and HRP entered the VVOs of normal venular endothelium because stomata joining vesicles and vacuoles to each other and to the lumen and ablumen were closed. VVOs and their component vesicles/vacuoles were readily distinguished from endosomal organelles such as coated vesicles and multivesicular bodies, which also accumulated FE and HRP. Our findings indicate that VVOs provide a major pathway for the extravasation of circulating macromolecules across endothelia taller than capillary endothelium and suggest that upregulated VVO function accounts for the well-known hyperpermeability of tumor blood vessels.

Animals↗
PubMed1987

A renal cell carcinoma neoplastic antigen detectable by immunohistochemistry is defined by a murine monoclonal antibody.

BALB/c mice were hyperimmunized with ACHN (ATCC CRL 1611, American Type Culture Collection, Rockville, Maryland), a stable in vitro cell line derived from a malignant pleural effusion in a 22-year-old man with renal cell carcinoma. The hyperimmune spleen cells were fused with NS-1 murine myeloma cells using polyethylene glycol. Hybridoma supernatants were screened for the presence of IgG reactive with detergent extracts of ACHN and nonreactive with detergent extracts of normal kidney tissue. A stable, rapidly growing clone named 5F4 was isolated. Supernatant from 5F4 was used as a primary antibody preparation for avidin-biotin complex immunoperoxidase staining of multiple cases of renal cell carcinoma, normal tissues, and other tumors. 5F4 produced IgG which reacted with a cytoplasmic structure in paraffin-embedded sections of all renal cell carcinomas tested. There was occasional, weak, granular, cytoplasmic staining of isolated tubular lining cells in adjacent normal kidney.

Animals↗
PubMed1979

Ultrastructural observations on the oogenesis of Triops cancriformis (Crustacea, Notostraca). II. Early developmental states of the oocyte.

The first stages of the oogenesis of Triops cancriformis have been studied. At the outset the oocyte is smaller than the nurse cells. Meiosis begins with typical synaptonemal complexes. The significance of these complexes and of some other peculiar structures of germ cells, i.e., pore complexes and annuli within the nucleus, and annulate lamellae within the cytoplasm are discussed. The morphofunctional uniformity of some cytoplasmic structures (annulate lamellae, concentrically arranged ER, and yolk globules) in the oocyte as well as its nurse cells is also discussed.

Animals↗
PubMed2004

Dynamics of Golgi matrix proteins after the blockage of ER to Golgi transport.

When the ER to Golgi transport is blocked by a GTP-restricted mutant of Sar1p (H79G) in NRK-52E cells, most Golgi resident proteins are transported back into the ER. In contrast, the cis-Golgi matrix proteins GM130 and GRASP65 are retained in punctate cytoplasmic structures, namely Golgi remnants. Significant amounts of the medial-Golgi matrix proteins golgin-45, GRASP55 and giantin are retained in the Golgi remnants, but a fraction of these proteins relocates to the ER. Golgin-97, a candidate trans-Golgi network matrix protein, is retained in Golgi remnant-like structures, but mostly separated from GM130 and GRASP65. Interestingly, most Sec13p, a COPII component, congregates into larger cytoplasmic clusters soon after the microinjection of Sar1p(H79G), and these move to accumulate around the Golgi apparatus. Sec13p clusters remain associated with Golgi remnants after prolonged incubation. Electron microscopic analysis revealed that Golgi remnants are clusters of larger vesicles with smaller vesicles, many of which are coated. GM130 is mainly associated with larger vesicles and Sec13p with smaller coated vesicles. The Sec13p clusters disperse when p115 binding to the Golgi apparatus is inhibited. These results suggest that cis-Golgi matrix proteins resist retrograde transport flow and stay as true residents in Golgi remnants after the inhibition of ER to Golgi transport.

Autoantigens↗
PubMed1985

Cellulose microfibril assembly and orientation: recent developments.

A brief history of the literature dealing with cellulose microfibril assembly is presented, and a current summary of cellulose microfibril synthesizing complexes among eukaryotic cells is given. Terminal complexes not described before include the following: linear terminal complexes (TCs) with three rows in Eremosphaera, Microdictyon and Chaetomorpha; globular terminal complexes in Ophioglossum, Psilotum, Equisetum and Gingko. Cellulose microfibril assembly in Acetobacter xylinum is described very briefly and compared with the process among eukaryotic cells. Particular emphasis on structures that may be involved in the spatial control of cellulose synthesis is given. Among these are cytoplasmic structures such as microtubules and microfilaments. Microfilament structures are shown to clearly surround individual microtubules that lie adjacent to the plasma membrane. Using freeze-fracture techniques, these labile associations have been shown for the first time. Microfibril orientation may be mediated through an interaction of cortical microtubules in association with microfilaments. A review of Mueller and Brown's membrane flow model for microfibril orientation is presented. Cellulose terminal complex clustering and its role in gravitropic response is covered. Definitive membrane changes with TC clustering/disaggregation and intramembranous particle frequencies, occur within 12 min following gravistimulation. These differences are pronounced in the cells from upper and lower hemicylinders of rapidly frozen tissue, which was studied by the freeze-fracture method. A hypothesis for cellulose microfibril interaction in controlling the constraint of the growth axis is presented, and the supporting data for terminal complex clustering/disaggregation as well as fluorescent brightener inhibition of the gravitropic response support this hypothesis. The onset and regulation of cellulose microfibril assembly is presented for synchronized protoplasts generated by Boergesenia, using inhibitors of transcription and translation. These results suggest dynamic turnover of terminal complex subunits during the assembly of the cellulose microfibril. This study is concluded with a brief discussion of possible phylogenetic trends in the evolution of cellulose synthesis. A principal underlying theme is that the specific arrangement and consolidation of the terminal complex subunits determine to a large degree the size and shape of the microfibril, its crystallinity, as well as intramicrofibrillar associations. Three basic types of TCs appear among all eukaryotic cells studied so far: namely, the rosette, the globular and the linear complex.

Cell Membrane↗
PubMed1998

Characterization of the p22 subunit of dynactin reveals the localization of cytoplasmic dynein and dynactin to the midbody of dividing cells.

Dynactin, a multisubunit complex that binds to the microtubule motor cytoplasmic dynein, may provide a link between dynein and its cargo. Many subunits of dynactin have been characterized, elucidating the multifunctional nature of this complex. Using a dynein affinity column, p22, the smallest dynactin subunit, was isolated and microsequenced. The peptide sequences were used to clone a full-length human cDNA. Database searches with the predicted amino acid sequence of p22 indicate that this polypeptide is novel. We have characterized p22 as an integral component of dynactin by biochemical and immunocytochemical methods. Affinity chromatography experiments indicate that p22 binds directly to the p150(Glued) subunit of dynactin. Immunocytochemistry with antibodies to p22 demonstrates that this polypeptide localizes to punctate cytoplasmic structures and to the centrosome during interphase, and to kinetochores and to spindle poles throughout mitosis. Antibodies to p22, as well as to other dynactin subunits, also revealed a novel localization for dynactin to the cleavage furrow and to the midbodies of dividing cells; cytoplasmic dynein was also localized to these structures. We therefore propose that dynein/dynactin complexes may have a novel function during cytokinesis.

Amino Acid Sequence↗
PubMed2006

Granular layer in the periplasmic space of gram-positive bacteria and fine structures of Enterococcus gallinarum and Streptococcus gordonii septa revealed by cryo-electron microscopy of vitreous sections.

High-resolution structural information on optimally preserved bacterial cells can be obtained with cryo-electron microscopy of vitreous sections. With the help of this technique, the existence of a periplasmic space between the plasma membrane and the thick peptidoglycan layer of the gram-positive bacteria Bacillus subtilis and Staphylococcus aureus was recently shown. This raises questions about the mode of polymerization of peptidoglycan. In the present study, we report the structure of the cell envelope of three gram-positive bacteria (B. subtilis, Streptococcus gordonii, and Enterococcus gallinarum). In the three cases, a previously undescribed granular layer adjacent to the plasma membrane is found in the periplasmic space. In order to better understand how nascent peptidoglycan is incorporated into the mature peptidoglycan, we investigated cellular regions known to represent the sites of cell wall production. Each of these sites possesses a specific structure. We propose a hypothetic model of peptidoglycan polymerization that accommodates these differences: peptidoglycan precursors could be exported from the cytoplasm to the periplasmic space, where they could diffuse until they would interact with the interface between the granular layer and the thick peptidoglycan layer. They could then polymerize with mature peptidoglycan. We report cytoplasmic structures at the E. gallinarum septum that could be interpreted as cytoskeletal elements driving cell division (FtsZ ring). Although immunoelectron microscopy and fluorescence microscopy studies have demonstrated the septal and cytoplasmic localization of FtsZ, direct visualization of in situ FtsZ filaments has not been obtained in any electron microscopy study of fixed and dehydrated bacteria.

Bacillus subtilis↗
PubMed1980

[L line cell differentiation. Histochemical and electron microscopic studies].

In a medium supplemented with 60 per cent large cattle serum, part of the cell population of L-transformed culture was seen to be differentiated into mature lipocytes. The formation of structures similar to normal fat tissue took place in the same conditions, provided a reduced quantity of the seeded cells was used. The cell differentiation was accompanied with a decrease in acid phosphatase and non-specific esterase activities. The ultrastructural study has demonstrated a suitable preservation of cytoplasmic structures and a domination of the rough cytoplasmic reticulum compared to the control cell cultures where free ribosomes and polysomes predominated.

Acid Phosphatase↗
PubMed1985

Neurons and terminals in the retrohippocampal region in the rat's brain identified by anti-gamma-aminobutyric acid and anti-glutamic acid decarboxylase immunocytochemistry.

The distribution of gamma-aminobutyric acid (GABA) containing nerve cells and terminals was studied at the light and electron microscopic levels in the retrohippocampal region of the rat by using anti-glutamic acid decarboxylase (GAD) and anti-GABA antibodies in immunocytochemistry. Large numbers of GAD and GABA stained cells were found in all retrohippocampal structures. At the ultrastructural level, the immunoreactivity against GABA and against the synthesizing enzyme GAD was localized to cytoplasmic structures, including loose clumps of rough endoplasmic reticulum, ribosomal arrays, outer mitochondrial surfaces and in axonal boutons. The GAD- and GABA-immunoreactive(-i) cells were found in all subfields of the retrohippocampal region (e.g., the subicular complex, the entorhinal area). Within the entorhinal area a slightly larger number of immunoreactive cells could be detected in layers II and III than in the other layers. In the subiculum, pre- and parasubiculum the GAD and GABA-i cells were present in relatively large numbers in all layers, except the molecular layer, which contained only a small number of GABA cells. Within the entorhinal area, GAD and GABA stained cells ranged in size from small (13 micron in diameter) to large (22 micron in diameter). A large number of different morphological classes of cells were found, except pyramidal and stellate cells. In the pre- and parasubiculum, on the other hand, the GABA cells were generally small to medium in size and morphologically more homogeneous than in the subiculum and entorhinal area. The entire retrohippocampal region was densely innervated by GABA preterminal processes, with little variation in the regional density of innervation. Within the entorhinal area, presubiculum and subiculum, a clear difference was found in the laminar pattern of innervation. In all three subfields the densest innervation was in layer II. In the entorhinal area both GAD- and GABA-i axons form palisades of fibers around the somata of neurons, which are tightly packed together in this layer. In the electron microscope both GAD-i and GABA-i were demonstrated in these axons. Axosomatic synaptic contacts were common between axons and the stellate neurons and other cells of this layer. Layers IV and VI appeared less dense in GAD-i terminals but appeared more densely innervated than layers III and V. The lamina dessicans was relatively poor in GAD-i. In the subiculum and presubiculum, as well as all other subfields of the hippocampal region, the innervation is dominated by axo-somatic innervation of layer II cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

One-dimensional diffusion on microtubules of particles coated with cytoplasmic dynein and immunoglobulins.

We characterized and compared the diffusion of beads coated with proteins such as cytoplasmic dynein, alpha-casein, and some immunoglobulins on microtubules. Such weak binding interactions could be common and convenient for concentrating proteins at the surface of cytoplasmic structures such as microtubules. In studying the motile behavior of anionic latex beads coated with limiting dilutions of cytoplasmic dynein, we observed that in addition to active movement, 20-50% of the beads moved back and forth in a random manner. The random movement was inhibited by depletion of ATP or addition of ADP or AMP-PNP. Mean-square-displacement analysis showed that the movement is a one-dimensional diffusion along the microtubule axis with a diffusion coefficient of 2.16 x 10(-10) cm2/sec. Histogram analysis of off-axis movements suggested that approximately 60% of the diffusing beads followed the path of a single microtubule protofilament. Beads coated with proteins such as alpha-casein or a monoclonal immunoglobulin were also observed to diffuse on microtubules with a similar diffusion coefficient to cytoplasmic dynein. However, alpha-casein or immunoglobulin-bead diffusion was not ATP dependent and did not follow the paths of single protofilaments. Thus, although the environment of the microtubule surface can trap a variety of different protein-coated beads, cytoplasmic dynein's interaction is unusual in its ATP dependence and tracking on a single protofilament, which is consistent with its specific interaction with microtubules. Diffusive interactions could concentrate associating proteins and still allow for freedom of movement.

Adenosine Diphosphate↗
PubMed1995

The biochemistry of programmed cell death.

Programmed cell death (PCD) is involved in the removal of superfluous and damaged cells in most organ systems. The induction phase of PCD or apoptosis is characterized by an extreme heterogeneity of potential PCD-triggering signal transduction pathways. During the subsequent effector phase, the numerous PCD-inducing stimuli converge into a few stereotypical pathways and cells pass a point of no return, thus becoming irreversibly committed to death. It is only during the successive degradation phase that vital structures and functions are destroyed, giving rise to the full-blown phenotype of PCD. Evidence is accumulating that cytoplasmic structures, including mitochondria, participate in the critical effector stage and that alterations commonly considered to define PCD (apoptotic morphology of the nucleus and regular, oligonucleosomal chromatin fragmentation) have to be ascribed to the late degradation phase. The decision as to whether a cell will undergo PCD or not may be expected to be regulated by "switches" that, once activated, trigger self-amplificatory metabolic pathways. One of these switches may reside in a perturbation of mitochondrial function. Thus, a decrease in mitochondrial transmembrane potential, followed by mitochondrial uncoupling and generation of reactive oxygen species, precedes nuclear alterations. It appears that molecules that participate in apoptotic decision-making also exert functions that are vital for normal cell proliferation and intermediate metabolism.

Apoptosis↗
PubMed1986

[Ultrastructural cytology of testicular seminomas].

The aim of this electron microscopic study was to analyze and compare aspects of various histologically distinct seminoma variants including the classical form (11 cases), anaplastic seminoma (1 case) and seminoma with syncytiotrophoblastic giant cells. Sub-microscopic features of these seminoma types are essentially the same; these various seminoma forms can not be electron microscopically distinguished. Although the cytoplasmic structures of the tumor cells varied, the most striking feature was a high glycogen content. Three types of seminoma cells could be distinguished on the basis of the relation between glycogen accumulation and cytoplasmic organelles: 1. tumor cells with plentiful glycogen and scant organelles, 2. tumor cells packed with organelles including RER, mitochondria and Golgi-apparatus but with finely dispersed glycogen, 3. tumor cells with numerous free ribosomes but few organelles and little glycogen. Glycogenosomes are described here for the first time as distinct organelles in seminoma cells, suggesting a disturbed carbohydrate metabolism. Another typical finding was a network of fine filaments measuring about 4 to 6 nm which probably correspond to actin. By interweaving in all directions they produce a felt-like meshwork on the inner-side of the cell membrane. Based on the composition of the seminoma cell cytoplasm with its collection of special organelles including lamellae annulatae, chromatoid bodies and crystalline structures resembling Lubarsch crystals, the tumor cells may be interpreted as neoplastic germ cells related to the so-called atypical germ cells of the testis.

Adult↗
PubMed2000

Mapping of the human CP49 gene and identification of an intragenic polymorphic marker to allow genetic linkage analysis in autosomal dominant congenital cataract.

The CP49 protein is an intermediate filament protein expressed specifically in the lens fibre cells of the lens, where it is an important cytoplasmic structural component. Dominant-negative mutations in other intermediate filament proteins, such as keratins, cause disorders characterised by dense cytoplasmic aggregates in specific cell types. The CP49 gene is therefore a good candidate for dominantly inherited forms of cataract. To allow genetic linkage analysis of families with autosomal dominant cataract with respect to CP49, a highly polymorphic intragenic microsatellite marker for this gene has been developed. In addition, both low and high resolution radiation hybrid mapping of the CP49 gene has been completed, placing it very close to microsatellite marker D3S1290 on human chromosome 3q. Furthermore, using the intragenic CP49 microsatellite, linkage was excluded in four families with genetically uncharacterized forms of autosomal dominant congenital cataract.

Base Sequence↗
PubMed1990

Ultrastructural modification of the plasma membrane in HUT 102 lymphoblasts by long-wave ultraviolet light, psoralen, and PUVA.

Ultrastructural alterations of the plasma membrane in HUT 102 lymphoblasts were assessed after a 2-h interaction with a suprapharmacologic (15 micrograms/ml) concentration of 8-MOP, 2-h irradiation with UVA (2.1 mW/cm2), and the exposure of the HUT 102 cells to PUVA under the same conditions. The dark reaction of HUT cells with 8-MOP resulted in the disappearance of microvilli, the emergence of plasma-membrane-associated spherical bodies, formation of lamellar fungiform membrane evaginations, and, in approximately 1% of the cells, formation of uropods and cell capping. Except for uropod formation and cell capping, UVA has induced the same plasma-membrane alterations, and was more deleterious to structural cytoplasmic integrity than 8-MOP. Morphologic changes of the plasma membrane in PUVA-exposed cells tended to replicate structural alterations elicited independently during the dark reaction by suprapharmacologic 8-MOP concentrations. Partial retention of microvilli by cells after PUVA was the sole exception. In light of all available evidence we conclude that psoralen during the dark reactions interacts with plasma membrane lipids by as yet undisclosed mechanisms and that in addition to lipids, membrane proteins are also the primary target of the initial interaction of HUT 102 cells with psoralen during PUVA treatment.

Cell Membrane↗
PubMedDate not supplied

[Fine structure of Chloroflexus aurantiacus var. mesophilus (nom. prof.) grown in the light under aerobic and anaerobic conditions].

The fine structure was studied in two mesophilic strains of Chloroflexus aurantiacus var. mesophilus (nom. prof.): KN-4 and BR-1. Trichomes are covered with a mucous fibrillar sheath which is more developed in the KN-4 strain. Photosynthetic structures, "chlorobium-vesicles", are located at the periphery of the cells of both strains. The structure of the cell was is typical of gram-negative microorganisms. By their electron density and dimensions, inner cytoplasmic structures are identified as poly-beta-hydroxybutyric acid, polyphosphates, and polysaccharides. When the strain BR-I was grown in aerobic conditions in the light, "chlorobium-vesicles" were not synthesized and intracytoplasmic membranes were represented by small tubular-vesicular invaginations. When the cells were grown under anaerobic conditions in the lgiht, numerous "chlorobium-vesicles" were formed, and additional large vesicular membrane systems appeared; these systems occupied over 20 per cent of the cell volume. Possible relationship between the membrane structures and the synthesis of bacteriochlorophyll a and c is discussed.

Aerobiosis↗
PubMed1996

Mechanism of oligonucleotide release from cationic liposomes.

We propose a mechanism for oligonucleotide (ODN) release from cationic lipid complexes in cells that accounts for various observations on cationic lipid-nucleic acid-cell interactions. Fluorescent confocal microscopy of cells treated with rhodamine-labeled cationic liposome/ fluorescein-labeled ODN (F-ODN) complexes show the F-ODN separates from the lipid after internalization and enters the nucleus leaving the fluorescent lipid in cytoplasmic structures. ODN displacement from the complex was studied by fluorescent resonance energy transfer. Anionic liposome compositions (e.g., phosphatidylserine) that mimic the cytoplasmic facing monolayer of the cell membrane released ODN from the complex at about a 1:1 (-/+) charge ratio. Release was independent of ionic strength and pH. Physical separation of the F-ODN from monovalent and multivalent cationic lipids was confirmed by gel electrophoresis. Fluid but not solid phase anionic liposomes are required, whereas the physical state of the cationic lipids does not effect the release. Water soluble molecules with a high negative linear charge density, dextran sulfate, or heparin also release ODN. However, ATP, spermidine, spermine, tRNA, DNA, polyglutamic acid, polylysine, bovine serum albumin, or histone did not release ODN, even at 100-fold charge excess (-/+). Based upon these results, we propose that the complex, after internalization by endocytosis, induces flip-flop of anionic lipids from the cytoplasmic facing monolayer. Anionic lipids laterally diffuse into the complex and form a charged neutralized ion-pair with the cationic lipids. This leads to displacement of the ODN from the cationic lipid and its release into the cytoplasm.

Base Sequence↗
PubMed1976

Intranuclear complexes in a copper-tolerant green alga.

The results of ultrastructural studies and transmission electron microscope microanalysis of two Scenedesmus strains experimentally exposed to copper sulfate are presented. A fine-structural examination of the cells revealed the presence of nuclear inclusions in the form of central dense-core complexes. Cytoplasmic structures resembling the intranuclear inclusions were occasionally found in the cells. TEM-X-ray microanalysis of these structures has provided evidence that the inclusions contain copper. It is concluded that their presence may be regarded as a detoxifying mechanism.

Cell Nucleolus↗
PubMed2005

Regulating inducible transcription through controlled localization.

Many signaling pathways regulate the activity of effector transcription factors by controlling their subcellular localization. Until recently, the cytoplasmic retention of inactive transcription factors was mainly attributed to binding partners that mask the nuclear localization signals (NLSs) of target proteins. Inactive transcription factors were thought to be exclusively cytoplasmic until their activation, after which the NLSs were unmasked to allow nuclear translocation. There is now a growing body of evidence, however, that challenges this simple model. This review discusses recent reports that suggest that inducible transcription factors can constantly shuttle between the cytoplasm and the nucleus, and that their apparent cytoplasmic retention can be achieved by binding partners that mask the NLSs, tether the transcription factor to cytoplasmic structures, or mark the transcription factor for proteasomal degradation. We also discuss the possibility that this more complex model of cytoplasmic retention might be applicable to a broader range of transcription factors and their associated signaling pathways.

Animals↗