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PubMed1976

Preovulatory Granulosa Cells and Steroidogenesis. An Ultrastructural Study in the Rhesus Monkey.

Granulosa cells of developing preovulatory follicles from ovaries of 6 rhesus monkeys were studied with the electron microscope. They did not contain the cytoplasmic structures known to be associated with steroidogenesis. Such structures were found only in the luteinized granulosa cells of atretic follicles in the preovulatory ovary. The preovulatory granulosa cells were rich in RNA, and the production of the liquor folliculi is probably their main function. The apparent contradiction between the present findings and those reported in incubation studies is discussed.

Animals↗
PubMed2004

The ammonium transporter RhBG: requirement of a tyrosine-based signal and ankyrin-G for basolateral targeting and membrane anchorage in polarized kidney epithelial cells.

RhBG is a nonerythroid member of the Rhesus (Rh) protein family, mainly expressed in the kidney and belonging to the Amt/Mep/Rh superfamily of ammonium transporters. The epithelial expression of renal RhBG is restricted to the basolateral membrane of the connecting tubule and collecting duct cells. We report here that sorting and anchoring of RhBG to the basolateral plasma membrane require a cis-tyrosine-based signal and an association with ankyrin-G, respectively. First, we show by using a model of polarized epithelial Madin-Darby canine kidney cells that the targeting of transfected RhBG depends on a YED motif localized in the cytoplasmic C terminus of the protein. Second, we reveal by yeast two-hybrid analysis a direct interaction between an FLD determinant in the cytoplasmic C-terminal tail of RhBG and the third and fourth repeat domains of ankyrin-G. The biological relevance of this interaction is supported by two observations. (i) RhBG and ankyrin-G were colocalized in vivo in the basolateral domain of epithelial cells from the distal nephron by immunohistochemistry on kidney sections. (ii) The disruption of the FLD-binding motif impaired the membrane expression of RhBG leading to retention on cytoplasmic structures in transfected Madin-Darby canine kidney cells. Mutation of both targeting signal and ankyrin-G-binding site resulted in the same cell surface but nonpolarized expression pattern as observed for the protein mutated on the targeting signal alone, suggesting the existence of a close relationship between sorting and anchoring of RhBG to the basolateral domain of epithelial cells.

Amino Acid Motifs↗
PubMed1985

Formation of a morphologically complex system by peroxidase-positive lysosomal elements in human monocytes.

Computer-aided three-dimensional reconstruction of serial ultrathin sections revealed that freshly prepared monocytes from human blood contained endogenous peroxidase (PO) not only in cytoplasmic granules, but also in long contorted tubules and in complex elements, which consisted of both tubular and granular components. The various PO-positive elements formed an intricate system, which was separate from all other cytoplasmic structures, including the endoplasmic reticulum and the Golgi apparatus. Because the PO-positive elements in monocytes are known to be primary lysosomes, which are involved in host defense mechanisms, we suggest that the antimicrobial functions of human blood monocytes are exerted by functionally and morphologically diverse subcompartments of a complex system rather than by separate uniform granules.

Adult↗
PubMed1989

Cytoplasmic antigen in hepatocytes of chimpanzees infected with non-A, non-B hepatitis virus or hepatitis delta virus: relationship to interferon.

We previously described a cytoplasmic antigen, detected by monoclonal antibodies, in hepatocytes of chimpanzees experimentally infected with the parenterally transmitted form of non-A, non-B hepatitis virus or with the hepatitis delta virus. The expression of this antigen appears to be a host-specified response to infection with these two hepatitis viruses but not with hepatitis A virus, hepatitis B virus or enterically transmitted non-A, non-B hepatitis virus. To determine whether this antigen, found in parallel with the hepatocyte cytoplasmic structures described previously, is associated with interferon, as suggested by others, we studied by immunofluorescence liver biopsies from chimpanzees treated with an interferon inducer or exogenous interferon for the presence of the antigen. In two hepatitis B virus carrier chimpanzees and one normal chimpanzee treated with the interferon inducer polyinosinic-polyribocytidylic acid-poly-l-lysine carboxymethylcellulose, the antigen became detectable in hepatocytes within 2 weeks of initiation of the treatment, remained detectable throughout the treatment and disappeared within 4 weeks after treatment was terminated. Electron microscopy revealed that the biopsies positive for the antigen exhibited the hepatocyte cytoplasmic changes; convoluted membranes and microtubular aggregates, identical to those described originally for chimpanzees infected with non-A, non-B hepatitis virus. The antigen was not detected in any of the biopsies from a control chimpanzee that received only the carboxymethylcellulose used to stabilize the interferon inducer. In addition, liver biopsies obtained from a hepatitis B virus carrier chimpanzee during treatment with exogenous human leukocyte interferon were found to be positive for the antigen as well.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Uncoating of vaccinia virus.

Input vaccinia virus deoxyribonucleoproteids with buoyant densities (in CsCl) very similar (if not identical) to those of viral cores have been found in large cytoplasmic structures in which viral DNA replication takes place. The deoxyribonucleoproteids consist of at least five major and two minor core proteins and viral DNA which is protected against DNase digestion. It is suggested that viral core-like deoxyribonucleoproteids rather than released DNA are used in vaccinia-infected cells both for delayed-early gene transcription and viral DNA replication.

Animals↗
PubMed2006

RNA interference effector proteins localize to mobile cytoplasmic puncta in Schizosaccharomyces pombe.

Ago1, Dcr1 and Rdp1 are the core components of the RNA interference (RNAi) apparatus in the fission yeast Schizosaccharomyces pombe. They function in distinct gene-silencing pathways that direct homology-dependent degradation of mRNA and modification of chromatin. In addition, Ago1 and Dcr1 regulate enactment of Cdc2-dependent cell cycle checkpoints. The ability of the RNAi apparatus to perform multiple roles in these divergent pathways is sure to require dynamic localization of Ago1, Dcr1 and/or Rdp1. Although limited information is available, comprehensive studies regarding the relative localizations of Ago1, Dcr1 and Rdp1 are lacking. To this end, we employed live-cell imaging and immunoelectron microscopy to study the intracellular localizations of these proteins. In contrast to previous reports, our study results indicate that the bulk of Ago1 and Dcr1 form stable complexes and are associated with large, mobile, highly dynamic cytoplasmic elements. The majority of Rdp1 is localized to the nucleus, but a pool of Rdp1 is associated with the same cytoplasmic structures. The movements of these structures were dependent upon ATP and intact microtubules. Recruitment of the RNAi core proteins to these structures was not dependent upon siRNAs. Together, our data indicate that the enzymes required for the initiation and effector phases of RNA-dependent gene silencing are concentrated in a common intracellular location, an arrangement that would be expected to result in highly efficient post-transcriptional gene silencing.

Base Sequence↗
PubMed1984

Some aspects of desmosomal morphology during differentiation of hamster cheek pouch epithelium.

Desmosomes function as intercellular attachment devices. In keratinised epithelia, squames are shed from the surface and these are replaced by less differentiated cells of the basal or parabasal layers, which migrate progressively towards the surface. In order to perform these migratory activities, cellular movement must occur, with the implication that cells must be able to make and break their desmosomal attachments. The present study investigates desmosomal ultrastructure with the objective of suggesting mechanisms by which desmosomes are altered during differentiation. The majority of desmosomes in basal, spinous and granular layers were similar in morphology, with differences being quantitative rather than qualitative. Desmosomes appeared to be more frequent and of smaller dimensions in granular cells when compared with those present on cells from lower strata. Upon keratinisation, desmosomal cytoplasmic structural specialisations disappeared and the intercellular contact layer became more prominent. A number of features which might represent desmosomal formation or synthesis were observed in nucleated cellular layers. These included an apparent budding or fusing of attachment plaques from existing desmosomes. Asymmetrical attachment plaques were prevalent with a markedly reduced number of tonofilaments associated with one plaque or an attachment plaque which was generally or locally reduced in electron density. Other appearances suggested that de novo desmosomal formation occurred as a result of the production of either single or paired attachment plaques, often containing fine filaments extending for a short distance into the cytoplasm. In view of the increased frequency of desmosomes in granular cells, the majority of these desmosomal abnormalities may represent synthetic rather than degradative activities.

Animals↗
PubMed2005

Xenopus Xpat protein is a major component of germ plasm and may function in its organisation and positioning.

In many animals, including Drosophila, C. elegans, zebrafish and Xenopus, the germ line is specified by maternal determinants localised in a distinct cytoplasmic structure called the germ plasm. This is consists of dense granules, mitochondria, and specific localised RNAs. We have characterised the expression and properties of the protein encoded by Xpat, an RNA localised to the germ plasm of Xenopus. Immunofluorescence and immunoblotting showed that this novel protein is itself a major constituent of germ plasm throughout oogenesis and early development, although it is also present in other regions of oocytes and embryos, including their nuclei. We found that an Xpat-GFP fusion protein can localise correctly in cultured oocytes, in early oocytes to the 'mitochondrial cloud', from which germ plasm originates, and in later oocytes to the vegetal cortex. The localisation process was microtubule-dependent, while cortical anchoring required microfilaments. Xpat-GFP expressed in late stage oocytes assembled into circular fields of multi-particulate structures resembling endogenous fields of germ plasm islands. Furthermore these structures could be induced to form at ectopic sites by manipulation of culture conditions. Ectopic Xpat-GFP islands were able to recruit mitochondria, a major germ plasm component. These data suggest that Xpat protein has an important role in Xenopus germ plasm formation, positioning and maintenance.

Actin Cytoskeleton↗
PubMed1993

Light and electron microscopic features of the rat vestibular ganglion cells.

The vestibular ganglion cells of the rat were characterized with regard to the cytoplasmic structure by light and electron microscopic observation. Light microscopy revealed four types of cells, depending upon the characteristics and distribution of Nissl granules. Electron microscopy gave a definite classification of these types by the arrangement and distribution of the roughly surfaced endoplasmic reticulum and neurofilament. The characteristics of the ganglion cells are discussed in relation to their size and function.

Animals↗
PubMed1977

Organization of cell junctions in the peritoneal mesothelium.

Intercellular junctions in the mesothelium of the visceral (mesentery and omentum), and parietal (diaphragm, pre-aortic, and iliac region) peritoneum were examined in rats and mice by using freeze-cleaved preparations. In addition to usual intercellular junctions (cell body junctions), special junctions are found between cell processes and the surface of the neighboring cell (cell process junctions). Cell body junctions are provided with tight junctions and communicating (gap) junctions. The former consist of one to two junctional strands which show a characteristic staggered arrangement, and focal discontinuities. In cell process junctions, the strands form loops or appear as short, free-ending elements; their polymorphism suggests considerable lability, probably in connection with their assembly and disassembly. The existence of free-ending strands indicates that such structures can be used as attachment devices without being concomitantly involved in the formation of occluding zonules. In both types of junctions, the strands can be resolved into bars, approximately 80- 100nm long, frequently provided with terminal enlargements and intercalated particles which occur singly or in small clusters. These particles are morphologically similar to those present in communicating (gap) junctions. The mesothelium is also provided with isolate composite macular junctions. Throughout the mesothelium, the cleavage plane follows the outer contour of junctional strands and particles, suggesting that strand-to-strand interactions in the apposed membranes are weaker than interactions between each strand and underlying cytoplasmic structures. In their general geometry and cleavage characteristics, the mesothelial junctions resemble the junctions found in the venular endothelium.

Animals↗
PubMed1982

Anti-golgi complex autoantibodies in a patient with Sjögren syndrome and lymphoma.

During routine immunofluorescence studies of the serum of a patient with Sjögren's syndrome and lymphoma we detected antibodies giving a cytoplasmic pattern which did not correspond to previously described patterns found for autoantibodies. Using different cells and tissues as substrates for indirect immunofluorescence, including rat liver, rat small bowel, rat testicle, human thyroid, guinea-pig plasma cells and cultured human fibroblasts, the cytoplasmic structure to which these autoantibodies are directed seems to be the golgi complex, a conclusion supported by histochemical studies. Furthermore, these antibodies were absorbed by isolated golgi vesicles. The autoantibodies are of IgG and IgA classes, and the antigen(s) with which they react is(are) resistant to treatment with DNAse and RNAse. None of the sera from 50 normal individuals, seven patients with Sjögren's syndrome (five of them primary and two associated with rheumatoid arthritis; none of them with lymphoma), 25 patients with mixed connective tissue disease, 10 patients with systemic lupus erythematosus and five patients with progressive systemic sclerosis, had antibodies directed against this cytoplasmic specificity, as determined by indirect immunofluorescence. This is the first time that autoantibodies directed to the golgi complex are reported. The significance of this finding awaits further descriptions in patients with a clinical picture similar to the one reported here.

Adult↗
PubMed1996

Dictyostelium discoideum cells lacking the 34,000-dalton actin-binding protein can grow, locomote, and develop, but exhibit defects in regulation of cell structure and movement: a case of partial redundancy.

Cells lacking the Dictyostelium 34,000-D actin-bundling protein, a calcium-regulated actin cross-linking protein, were created to probe the function of this polypeptide in living cells. Gene replacement vectors were constructed by inserting either the UMP synthase or hygromycin resistance cassette into cloned 4-kb genomic DNA containing sequences encoding the 34-kD protein. After transformation and growth under appropriate selection, cells lacking the protein were analyzed by PCR analyses on genomic DNA, Northern blotting, and Western blotting. Cells lacking the 34-kD protein were obtained in strains derived from AX2 and AX3. Growth, pinocytosis, morphogenesis, and expression of developmentally regulated genes is normal in cells lacking the 34-kD protein. In chemotaxis studies, 34-kD- cells were able to locomote and orient normally, but showed an increased persistence of motility. The 34-kD- cells also lost bits of cytoplasm during locomotion. The 34-kD- cells exhibited either an excessive number of long and branched filopodia, or a decrease in filopodial length and an increase in the total number of filopodia per cell depending on the strain. Reexpression of the 34-kD protein in the AX2-derived strain led to a "rescue" of the defect in the persistence of motility and of the excess numbers of long and branched filopodia, demonstrating that these defects result from the absence of the 34-kD protein. We explain the results through a model of partial functional redundancy. Numerous other actin cross-linking proteins in Dictyostelium may be able to substitute for some functions of the 34-kD protein in the 34-kD cells. The observed phenotype is presumed to result from functions that cannot be adequately supplanted by a substitution of another actin cross-linking protein. We conclude that the 34-kD actin-bundling protein is not essential for growth, but plays an important role in dynamic control of cell shape and cytoplasmic structure.

Actins↗
PubMed2003

Importance of nuclear localization of apoptin for tumor-specific induction of apoptosis.

The chicken anemia virus-derived protein Apoptin induces apoptosis specifically in human tumor and transformed cells and not in normal, untransformed cells. The cell killing activity correlates with a predominantly nuclear localization of Apoptin in tumor cells, whereas in normal cells, it is detected mainly in cytoplasmic structures. To explore the role of nuclear localization for Apoptin-induced cell death in tumor cells, we employed a mutagenesis strategy. First, we demonstrated that the C terminus of Apoptin contains a bipartite-type nuclear localization signal. Strikingly, further investigation showed that Apoptin contains two different domains that induce apoptosis independently, and for both domains, we found a strong correlation between localization and killing activity. Using inhibitors, we ruled out the involvement of de novo gene transcription and translation and further showed that Apoptin itself does not have any significant transcriptional repression activity, suggesting that Apoptin exerts its effects in the nucleus by some other method. To determine whether nuclear localization is sufficient to enable Apoptin to kill normal, untransformed cells, we expressed full-length Apoptin fused to a heterologous nuclear localization signal in these cells. However, despite its nuclear localization, no apoptosis was induced, which suggests that nuclear localization per se is not sufficient for Apoptin to become active. These studies increase our understanding of the molecular pathway of Apoptin and may also shed light on the mechanism of cellular transformation.

Active Transport, Cell Nucleus↗
PubMed1999

Microfilament-dependent modulation of cytoplasmic protein binding to TNFalpha mRNA AU-rich instability element in human lymphoid cells.

Cytoplasmic proteins with binding capability to AU-rich instability determinant sequences (ARE) of tumour necrosis factor alpha (TNFalpha) mRNA 3' untranslated region (3'UTR) were assessed in human lymphoid cells. In vitro label transfer experiments using wild type as well as mutant sequences in which the 70 nucleotide-long AUUUA pentamer-containing portion of the 3'UTR had been deleted conferred binding specificity to five major activities of 22/25-, 38/40-, 50-, 60- and 80-kDa proteins in cytoplasmic extracts of peripheral blood mononuclear cells (PBMCs). Cytochalasin-induced disarrangement of the F-actin-based microfilament system led to a Triton X-100-insoluble to soluble redistribution of these binding activities. No such changes were observed in Jurkat tumour cells. Combination of in vivo UV-crosslinking and in vitro label transfer experiments revealed considerable differences in RNA association between proteins of the same cell type as well as between proteins of identical molecular weight (Mw) derived from either PBMCs or Jurkat cells. Our findings may explain some aspects of differential regulation of interleukin 2 (IL-2) and TNFalpha mRNA stability upon microfilament disruption in human PBMCs observed in an earlier study. These results also suggest that the physical state of cytoplasmic structural environment might contribute to important regulatory processes regarding key elements of eukaryotic mRNA metabolism, such as modulation of stability. Finally, these data highlight the possibility that the often observed disorganization of the cytoskeleton in tumour cells may partly be responsible for the maintenance of the neoplastic state, a phenomenon that potentially involves ARE-AUBP interactions.

3' Untranslated Regions↗
PubMed1971

Cytochemistry, cytogenetics and ultrastructure of hamster tumour cells carrying mouse sarcoma viral genome (HT-1 cells).

The pleomorphic cytology of the HT-1 cell line is described. Cytochemical studies indicated the presence of glycogen and lysosomes in these cells. Cytogenetic studies demonstrated the presence of a large telocentric chromosome (M1) and two minute chromosomes (M2) not found in normal hamster cells. A cloned line was isolated which did not contain these marker chromosomes. All cells were hyperdiploid with chromosome number around triploidy, although none was a true triploid. Ultrastructural studies revealed the presence of "nuclear bodies", "dense bodies" and "interchromatinic granules" which have been previously described in viral induced malignancies. A few of the cells contained in their cytoplasm structures of approximately 700 [unk] in diameter which bore some resemblance to immature virus particles. Both light and electron microscopy demonstrated some nuclei lacking chromatin aggregates. This is interpreted to mean that the total genetic material of these nuclei was dispersed as free DNA not linked with histone to form chromatin aggregates.

Animals↗
PubMed2001

Antiendothelial antibodies in sera of patients with infective endocarditis.

Infective endocarditis is characterized by the colonization of endocardium by microorganisms. Except for Staphylococcus aureus, microorganisms are not able to adhere to and grow on endocardial cells; prior damage, e.g., by shear stress or other mechanical factors, is necessary. But other causes may well have a share. This study was, therefore, designed to identify immunological factors, especially antibodies against endothelial cells, which could contribute to the initiation of endocardial injury. Sera of patients with infective endocarditis and healthy controls were investigated for the presence of antibodies against endothelial antigen. As the antigen source human umbilical vein endothelial cells were used. Antibodies against endothelial cells were detected by indirect immunofluorescence, ELISA, immunoblotting, antibody dependent cellular cytotoxicity, and antibody mediated cytotoxicity. Antibodies against endothelial cells were found in seven out of fifteen patients. These antibodies were directed against cytoplasmic structures and only appeared in the course of the disease. A correlation between the presence of these antibodies and disease activity or the outcome of disease was not observed. These antibodies may develop as a consequence of damage to endocardial cells (thereby exposing intracellular antigen to the immune system) and do not seem to play a role in the pathogenesis of infective endocarditis.

Antibodies↗
PubMed1989

The fine structure of acquired immunodeficiency syndrome encephalopathy.

Involvement of the central nervous system with the human immunodeficiency virus is thought to underlie the clinical and pathologic features of acquired immunodeficiency syndrome (AIDS) encephalopathy. Although morphologic, immunocytochemical, and molecular data point to predominant human immunodeficiency virus infection of multinucleated and mononuclear macrophages, neuroglial and other cells are thought to be involved as well. Electron microscopic studies of biopsy tissue that might further define the neuropathologic changes have been limited. The opportunity to study well-preserved biopsy tissue from a 38-year-old man with the acute onset of dementia and AIDS encephalopathy prompted this report. Human immunodeficiency virus was seen budding from the surface of multinucleated and mononuclear cells with morphologic features of macrophages; a rare astrocyte process showed evidence of viral infection as well. Macrophages were noted within the walls of blood vessels and in intimate contact with lymphocytes within the neuropil. Notably rare were tubuloreticular inclusions, interferon-related cytoplasmic structures commonly found in systemic endothelial cells and lymphocytes in AIDS. Their relative scarcity may signify reduced interferon production in AIDS encephalopathy.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Association of RNase mitochondrial RNA processing enzyme with ribonuclease P in higher ordered structures in the nucleolus: a possible coordinate role in ribosome biogenesis.

RNase mitochondrial RNA processing enzyme (MRP) is a nucleolar ribonucleoprotein particle that participates in 5.8S ribosomal RNA maturation in eukaryotes. This enzyme shares a polypeptide and an RNA structural motif with ribonuclease P (RNase P), a nuclear endoribonuclease originally described in the nucleus that processes RNA transcripts to generate their mature 5' termini. Both enzymes are also located in mitochondria. This report further characterizes the relationship between RNase MRP and RNase P. Antisense affinity selection with biotinylated 2'-O-methyl oligoribonucleotides and glycerol gradient fractionation experiments demonstrated that small subpopulations of RNase MRP and RNase P associate with each other in vivo in macromolecular complex, possibly 60-80S preribosomes. This latter notion was supported by fluorescence in situ hybridization experiments with antisense oligonucleotides that localized that RNA components of RNase MRP and RNase P to the nucleolus and to discrete cytoplasmic structures. These findings suggest that small subpopulations of RNase MRP and RNase P are physically associated, and that both may function in ribosomal RNA maturation or ribosome assembly.

Base Sequence↗