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PubMed1981

Scanning and transmission electron microscope studies on the organ of Corti and stria vascularis in human fetal cochlear ducts.

The organ of Corti in human fetuses aged 5 and 7 months, respectively, was observed with the scanning and transmission electron microscope (SEM and TEM). By SEM observation, bulbous cytoplasmic structures protruding from the apical surface of the outer and inner hair cells were observed as was the case in SEM reports by others. By TEM observation, it was revealed that these structures are cytoplasmic projections from the so-called cuticular notch which, in adults, houses the basal body and is a site for synthesis of auditory stereocilia and a single kinocilium. The stria vascularis was examined only in the 5 month specimen. The cytoplasm of the differentiating marginal cells is characterized by the presence of thick walled tubular membranes. The observation suggests that this tubular system may represent "a particular site" for secretion of some ions into the endolymph in the fetal condition.

Cochlea↗
PubMed2002

Cytoplasmic surface structures of bacteriorhodopsin modified by site-directed mutations and cation binding as revealed by 13C NMR.

We have examined how cytoplasmic surface structures of [3-(13)C]Ala-labeled bacteriorhodopsin (bR), consisting of the C-terminal alpha-helix and cytoplasmic loops, are altered by site-directed mutations at the former (R227Q) and the latter (A160G, E166G, and A168G) and by cation binding, by means of displacements of the (13)C NMR peaks of Ala228 and Ala233 (C-terminal alpha-helix), Ala103 (C-D loop), and Ala160 (E-F loop). Cytoplasmic ends of the B and F helices were found to undergo fluctuation motions on the order of 10(-5) s, when such surface structures were disrupted, as viewed from suppressed (13)C NMR signals. This happens also for deionized blue membranes of wild type and A160G, with accelerated fluctuations in the loops. Further, cytoplasmic surface structures of Na(+)-regenerated purple membrane from the blue membrane were significantly modified by Ca(2+) ions up to 1 mM under relatively low ionic strength of 10 mM NaCl, although they are very similar at high ionic strength (100 mM NaCl). To interpret these findings, the following two surface structures were proposed. The C-terminal alpha-helix of the wild type at ambient temperature is involved in a perturbed type, probably tilted toward the direction of the B and F helices, to prevent unnecessary fluctuations of these helices for efficient proton uptake during the photocycle. An unperturbed type of helix is achieved when such a surface structure was disrupted at low temperature or in an M-like state. This view is consistent with previously published data for the "proton binding cluster" consisting of Asp104, Glu166, and Glu234.

Alanine↗
PubMed2003

Reovirus sigma NS and mu NS proteins form cytoplasmic inclusion structures in the absence of viral infection.

Reovirus replication occurs in the cytoplasm of infected cells and culminates in the formation of crystalline arrays of progeny virions within viral inclusions. Two viral nonstructural proteins, sigma NS and micro NS, and structural protein sigma 3 form protein-RNA complexes early in reovirus infection. To better understand the minimal requirements of viral inclusion formation, we expressed sigma NS, mu NS, and sigma 3 alone and in combination in the absence of viral infection. In contrast to its concentration in inclusion structures during reovirus replication, sigma NS expressed in cells in the absence of infection is distributed diffusely throughout the cytoplasm and does not form structures that resemble viral inclusions. Expressed sigma NS is functional as it complements the defect in temperature-sensitive, sigma NS-mutant virus tsE320. In both transfected and infected cells, mu NS is found in punctate cytoplasmic structures and sigma 3 is distributed diffusely in the cytoplasm and the nucleus. The subcellular localization of mu NS and sigma 3 is not altered when the proteins are expressed together or with sigma NS. However, when expressed with micro NS, sigma NS colocalizes with mu NS to punctate structures similar in morphology to inclusion structures observed early in viral replication. During reovirus infection, both sigma NS and mu NS are detectable 4 h after adsorption and colocalize to punctate structures throughout the viral life cycle. In concordance with these results, sigma NS interacts with mu NS in a yeast two-hybrid assay and by coimmunoprecipitation analysis. These data suggest that sigma NS and mu NS are the minimal viral components required to form inclusions, which then recruit other reovirus proteins and RNA to initiate viral genome replication.

Animals↗
PubMed2003

52 kD Ro/SS-A localizes to punctate structures in the cytoplasm of epithelial cells.

Autoantibodies directed against 52 kD and 60 kD Ro/SS-A are frequently found in the sera of patients with lupus erythematosus and Sjögren's syndrome-related disorders. Their location in the cell is subject to continuous debate in literature. It has been postulated that 52 kD Ro (52 Ro) co-localizes with the 60 kD Ro autoantigen in the nucleus, while others demonstrated that 52 Ro is primarily cytoplasmic. In order to resolve this controversy, 52 Ro protein was tagged with green fluorescence protein, overexpressed in A431 keratynocytes, and its location determined using fluorescence confocal microscopy. The intracellular location of the fusion protein was revealed via GFP autofluorescene and indirect immunofluorescence microscopy, using purified anti-52 Ro antibodies. The cellular locations of native 52 Ro in normal human keratinocytes, and in human A431 keratinocyte and HepG2 hepatocyte cell lines were similarly determined by utilizing 2 human anti-52 Ro antibodies purified from two different non-overlapping fragments of recombinant 52 Ro. In addition, colocalization of 52 Ro with mitochondria, lysosomes and endosomes was evaluated. It was found that both the 52 Ro-GFP fusion protein and the native 52 Ro localize in discrete cytoplasmic punctate structures separately from the mitochondria, lysosomes and endosomes. Furthermore, human autoantibodies that are reactive with denaturation-sensitive epitopes on 52 Ro recognize these cytoplasmic punctate structures, whereas antibodies directed against denaturation-resistant 52 Ro epitopes do not. This explains why the previously used antibody against denaturation-resistant 52 Ro epitopes failed to detect the protein in such punctate structures.

Autoantigens↗
PubMed1986

Probing the structure of cytoplasm.

We have used size-fractionated, fluorescent dextrans to probe the structure of the cytoplasmic ground substance of living Swiss 3T3 cells by fluorescence recovery after photobleaching and video image processing. The data indicate that the cytoplasm of living cells has a fluid phase viscosity four times greater than water and contains structural barriers that restrict free diffusion of dissolved macromolecules in a size-dependent manner. Assuming these structural barriers comprise a filamentous meshwork, the combined fluorescence recovery after photobleaching and imaging data suggest that the average pore size of the meshwork is in the range of 300 to 400 A, but may be as small as 200 A in some cytoplasmic domains.

Animals↗
PubMed1981

Uptake and apparent digestion of cytoplasmic organelles by protein bodies (protein storage vacuoles) in mung bean cotyledons.

The large protein bodies of the storage parenchyma cells of mung bean (Vigna radiata) cotyledons contain vesicles measuring 0.2 to 2.0 mum in diameter. The vesicles contain ribosomes, ribosomes, membranous elements which may be derived from the endoplasmic reticulum and occasionally Golgi bodies and mitochondria. The vesicles can be seen by transmission electron microscopy in thin sections of plastic embedded specimens and in replicas of freeze-fractured preparations. Serial sections show that the vesicles are completely separated from the protein body membrane and are not invaginations of that membrane. Vesicles with cytoplasmic structures are seen most frequently in 2 to 4 day old seedlings. The vesicles may be formed when undulations of the protein body membrane are so deep as to permit the pinching-off of a portion of the cytoplasm, resulting in its subsequent isolation from the cytoplasm within the protein body. The digestion of the storage protein in the protein body is accompanied by the disappearance of the ribosomes and the membranous elements in the vesicles. We interpret this disappearance of the cytoplasmic structures in the vesicles as being due to their digestion by the protein body hydrolases (ribonuclease, proteinase and lipolytic enzymes). The uptake of cytoplasmic structures by the protein bodies continues after the reverse proteins have been digested. Cytochemical staining shows that the protein bodies and especially the vesicles are rich in acid phosphatase, a known marker of lytic activity in cells. The evidence presented here indicates that the protein bodies are the intracellular sites at which the digestion of cytoplasmic structure occurs. Protein bodies should therefore be considered not only as compartments for the hydrolysis of the stored protein, but also as autophagic organelles involved in the degradation of cytoplasmic macromolecules. The term protein bodies is well established, but the term protein storage vacuoles may describe these organelles more precisely.

Cytoplasm↗
PubMed1999

Structure of Cytoplasmic Polyhedrosis Virus from Bombyx mori.

The structures of full and empty capsids of CPV were studied by negative staining and electron cryomicroscopy and computer reconstruction techniques. By comparing the structures and biochemical compositions, the CPV was identified as a single-layered capsid with its five structural proteins located on it. This single capsid is arranged according to T=1 icosahedral symmetry with 12 turret-like spikes at its icosahedral vertices. The empty and full CPV show identical capsid but differ inside. The dense and ordered genomic dsRNA is located inside the full CPV. The internal space of the empty CPV has almost no electron density except for 12 electron densities attributed the transcriptional enzyme complexes extending inward from the base part of CPV spikes.

Journal Article↗
PubMedDate not supplied

[Functional state of cytoplasmic reticulum of hepatocytes in rats with acute kidney insufficiency].

In acute rat kidney insufficiency, caused by bilateral nephrectomy or ureter ligation, functional activity of hepatocyte cytoplasmic structure was decreased. Estimation of the cytoplasmic structures functional state included studies of hexenal anesthesia duration, determination of cytochromes P-450 and b5 content in liver microsomal fraction as well as of activities of amidopyrine-N-demethylase and aniline hydroxylase. The alterations of these parameters occurred apparently due to the effect of high concentrations of urea on liver tissue.

Acute Kidney Injury↗
PubMed1981

Cytoplasmic tubular structures in the diagnosis of oral discoid lupus erythematosus.

Biopsies from oral lesions of 5 patients with discoid lupus erythematosus (DLE), 5 with lichen planus (LP), 5 with leukoplakia (LEUK) and 3 patients with uncertain diagnoses termed DLE?, LP? were examined in the electron microscope for presence of cytoplasmic tubular structures (CTS) in vascular endothelium. Five vessels were examined in each of two randomly selected sections from each biopsy, without knowledge of the clinical diagnosis. All five DLE biopsies showed presence of CTS in 4-9 out of 10 vessels, as compared with none of 10 vessels in biopsies from LP or LEUK, the difference being significant. Further, CTS occurred in 4 out of 10 vessels in one DLE?, LP? biopsy from a patient with serologic signs of systemic lupus erythematosus. As CTS seem to be absent in oral lesions of LP and LEUK, which are the most important differential diagnoses for oral DLE, the identification of CTS in vascular endothelium sing electron microscopy may be an auxiliary diagnostic procedure in oral DLE.

Adult↗
PubMed2003

The Na+/H+ exchanger cytoplasmic tail: structure, function, and interactions with tescalcin.

We characterized the regulatory cytoplasmic tail of the Na(+)/H(+) exchanger using a histidine-tagged protein containing the C-terminal 182 amino acids (His182). Both tescalcin and calmodulin, two Na(+)/H(+) exchanger binding proteins, bound to the His182 protein. Cascade blue was used to label the His182 protein. Calcium caused an increase in fluorescence, suggesting exposure of the label on the protein to a more hydrophilic environment. Decreasing external pH caused a transient increase in cascade blue fluorescence, followed by a decrease in fluorescence of the cascade blue labeled Na(+)/H(+) exchanger C-terminus. Tescalcin caused a decrease in fluorescence by labeled His182 protein, and calcium reversed this effect. Expression of tescalcin in vivo inhibited activity of the Na(+)/H(+) exchanger when there was an intact C-terminus of the protein. We examined the CD spectra of His182 in the presence and absence of tescalcin. The C-terminal amino acids demonstrated a very small amount of alpha-helical structure and much more beta-sheet and beta-turn. This was not greatly affected by the presence of tescalcin, but calcium caused an increase in the amount of beta-structure and a decrease in the unstructured proportion of the protein. Sedimentation equilibrium analysis demonstrated that the C-terminal 182 amino acids exist predominantly as a monomer. The results suggest that the C-terminus of the Na(+)/H(+) exchanger exists primarily as a monomeric protein that binds regulatory tescalcin and can change conformation depending on pH and calcium. Conformation changes in this region of the protein may be responsible for altering the pH sensitivity of the intact Na(+)/H(+) exchanger.

Amino Acid Sequence↗
PubMed1980

Evidence that ADH-stimulated intramembrane particle aggregates are transferred from cytoplasmic to luminal membranes in toad bladder epithelial cells.

In freeze-fracture (FF) preparations of ADH-stimulated toad urinary bladder, characteristic intramembrane particle (IMP) aggregates are seen on the protoplasmic (P) face of the luminal membrane of granular cells while complementary parallel grooves are found on the exoplasmic (E) face. These IMP aggregates specifically correlate with ADH-induced changes in water permeability. Tubular cytoplasmic structures whose membranes contain IMP aggregates which look identical to the IMP aggregates in the luminal membrane have also been described in granular cells from unstimulated and ADH-stimulated bladders. The diameter of these cytoplasmic structures (0.11 +/- 0.004 micrometers) corresponds to that of tubular invaginations of the luminal membrane seen in thin sections of ADH-treated bladders (0.13 +/- 0.005 micrometers). Continuity between the membranes of these cytoplasmic structures (which are not granules) and the luminal membrane has been directly observed in favorable cross-fractures. In FF preparations of the luminal membrane, these apparent fusion events are seen as round, ice-filled invaginations (0.13 +/- 0.01 micrometer Diam), of which about half have the characteristic ADH-associated aggregates near the point of membrane fusion. They are less numerous than, but linearly related to, the number of aggregates counted in the same preparations (n = 78, r = 0.71, P less than 0.01). These observations suggest that the IMP aggregates seen in luminal membrane after ADH stimulation are transferred preformed by fusion of cytoplasmic with luminal membrane.

Animals↗
PubMed1989

Casein accumulation in distended rough endoplasmic reticulum of collagen gel-cultivated mouse mammary epithelia.

Mouse mammary epithelial cells cultivated on collagen gels synthesize and secrete casein in a hormone-dependent manner. Fine-structure electron microscopy of secretory cultures revealed numerous cytoplasmic structures surrounded by membrane that is studded with ribosomes. The structures appear to be distended rough endoplasmic reticulum (RER). Electron microscope protein A-colloidal gold immunolocalization showed casein antiserum-specific deposition of gold particles over the RER cytoplasmic vesicles in cells provided insulin, prolactin, and hydrocortisone (IPF). Nonimmune antiserum showed no gold particle deposition over these cytoplasmic structures. Epithelia provided only insulin showed no such cytoplasmic vesicles nor any specific deposition of gold particles. Immunoblot analysis of cell lysate and culture medium showed casein only in IPF-treated cultures. It appears that the casein secretory pathway in collagen gel cultured mammary epithelia is blocked at the step that fuses RER vesicles to Golgi membrane. The data raise questions regarding the processing and maturation of casein and the mechanism of casein secretion in these cultures.

Animals↗
PubMed1990

Culture of human endometrial cells under polarizing conditions.

Glandular epithelial and stromal cells were isolated from human endometrial biopsies and cultured in a dual-chambered system (Millicell; Millipore, Bedford, Ma., USA) that provides access of the medium to both sides of a membrane coated with reconstituted basement membrane material (Matrigel; Collaborative Research Inc., Bedford, Ma., USA). Examination by electron microscopy revealed that the epithelial cells formed a polarized cuboidal-columnar monolayer on the Matrigel surface. The cells exhibited apical microvilli, basal nuclei, and numerous cytoplasmic structures consistent with a well-differentiated cytoplasm; they were joined basally by interdigitating processes and apically by tight junctions and desmosomes. In contrast, epithelial cells cultured in parallel on plastic dishes were flattened, had fewer microvilli and cytoplasmic structures, and no junctional complexes.

Basement Membrane↗
PubMed1990

Peripheral airway cell differentiation in human lung cancer cell lines.

Clara cells and type II pneumocytes are the progenitor cells of the bronchioles and alveoli, respectively. These peripheral airway cells (PAC) contain characteristic cytoplasmic structures and express surfactant associated proteins. PAC cell markers are expressed by many pulmonary adenocarcinomas having papillary and/or lepidic growth patterns, which are characteristics of the bronchioloalveolar and papillary subtypes. We investigated the expression of PAC markers in a panel of 41 lung cancer cell lines. Ultrastructural studies demonstrated the presence of cytoplasmic structures characteristic of Clara cells or of type II pneumocytes in 9 of 34 (26%) non-small cell lung cancer cell lines, including 7 of 17 (41%) adenocarcinomas, one squamous cell carcinoma, and one large cell carcinoma. Of interest, the cytoplasmic structures were present in 5 of 6 (83%) cell lines initiated from papillolepidic adenocarcinomas. In addition, we examined the lines for expression of the surfactant associated proteins SP-A, SP-B, and SP-C. Eight of the nine cell lines containing cytoplasmic inclusions characteristic of PAC cells also expressed protein and/or RNA of SP-A, the major surfactant associated protein. Five of these lines expressed SP-B RNA (either constitutively or after dexamethasone induction), while a single line expressed SP-C only after dexamethasone induction. None of six small cell lung cancer cell lines examined expressed any of the PAC markers. Thus, PAC markers are expressed frequently (but not exclusively) in pulmonary adenocarcinoma cell lines, especially in those initiated from tumors having papillolepidic growth patterns. The establishment and identification of multiple cell lines expressing PAC features provide an important new resource for biological and preclinical therapeutic studies.

Adenocarcinoma↗
PubMed1988

Activation induces a rapid reorganization of spectrin in lymphocytes.

Lymphocyte activation results in a rapid reorganization of the cytoskeletal protein spectrin. Immediately following an activation signal, there is fragmentation of a spectrin-rich cytoplasmic structure and subsequent translocation of the fragments to defined areas of the plasma membrane in both antigen-specific T cell hybridomas and lymph node T cells. These dramatic changes have been documented by light and electron microscopic immunolocalization and by immunoblot analysis of plasma membrane-enriched preparations. A T cell hybridoma variant lacking the spectrin-rich cytoplasmic structure of the parental line does not redistribute spectrin and produces little or no IL-2 in response to antigen-dependent activation. This suggests a functional link between spectrin distribution and activation potential. We propose that the cytoplasmic structure functions as an organizing center or reservoir for spectrin that is sensitive to signaling at the cell surface.

Animals↗