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At least 865 records · Page 48Linked to original sources
PubMed1984

[A 45 kDa phosphorylated protein, resistant to alkaline treatment, appears at the time of rupture of the nuclear envelope during the 1st meiotic division of the Xenopus oocyte].

Xenopus oocytes were prelabeled with 32PO4 and induced to mature by progesterone treatment (1 microM). At the time of the breakdown of the germinal vesicle (nucleus), an alkali stable 45 kDa phosphoprotein appears in the 165 000 X g oocyte supernatant. Phospho-amino acid analysis shows that the 45 kDa protein is phosphorylated at threonine residues.

Animals↗
PubMed1978

Passive electrical properties of cultured murine lymphoblast (L5178Y) with reference to its cytoplasmic membrane, nuclear envelope, and intracellular phases.

Dielectric dispersion measurements over a frequency range 0.01-100 MHz were made with the suspensions of a cultured cell line, mouse lymphoma L5178Y, and an attempt to explain the observed dielectric behavior by taking explicitly into consideration the possible involvement of cell nucleus has been presented. The use of a conventional "single-shell" model in which the cell is represented by a homogeneous sphere coated with a thin limiting shell phase did not duplicate the observed dispersion curves, whereas a "double-shell" model in which one additional concentric shell is incorporated into the "single-shell" model gave a much better fit between the observed and the predicted dispersion curves. Based on the latter model, we analyzed the raw data of dielectric measurements to yield a set of plausible electrical parameters for the lymphoma cell: CM approximately or equal to 1.0 muF/cm2, CN approximately or equal to 0.4 muF/cm2, epsilonk approximately or equal to 300, kc/ka approximately to or equal to 0.9, and kk/kc approximately or equal to 0.7. Here, CM and CN are the specific capacities of plasma and nuclear membranes; epsilon and k are the dielectric constant and conductivity with subscript a, c and k referring respectively to the extracellular, the cytoplasmic and the karyoplasmic phases.

Cell Line↗
PubMed1988

Intracellular transport of VSV G protein occurs in cells lacking a nuclear envelope.

The intracellular transport of the G protein of a temperature sensitive vesicular stomatitis virus (VSV) mutant (ts 045) was examined in nucleated chinese hamster ovary (CHO) cells and in CHO cells subjected to enucleation with cytochalasin B. Although protein synthesis was virtually unaffected, enucleated cells synthesized only 30-45% of the amount of G protein assembled in control cells. As measured by acquisition of endoglycosidase H resistance, the rate of transport of the G protein from the RER to the medial golgi was found to be similar for nucleated and enucleated cells (t1/2 = 15 min). These data suggest that elements of the RER may directly transfer their contents to the Golgi, without the obligatory involvement of an intact NE.

Animals↗
PubMed1987

A monoclonal antibody against the nucleus reveals the presence of a common protein in the nuclear envelope, the perichromosomal region, and cytoplasmic vesicles.

A monoclonal antibody that recognizes antigenic determinants on the nucleus of cultured mammalian cells was isolated. Immunofluorescence studies using this antibody showed that the recognized antigen was present not only on the nucleus but also in cytoplasmic vesicles of interphase cells and in the perichromosomal region of mitotic cells. Premature chromosome condensation analysis showed that the reactive site for this monoclonal antibody could be detected in the perichromosomal region during the G2 and M phases, but not during the G1 and S phases. Finally, immunoblot analysis showed that this monoclonal antibody prepared against the nucleus recognized a protein of approximately 40 kD both in the cytoplasm and in the perichromosomal regions.

Animals↗
PubMed1985

An adenovirus 2-coded tumor antigen located on the endoplasmic reticulum and nuclear envelope is required for growth of transformed cells in Ca2+-deficient media.

Rat embryo cell lines containing the adenovirus 2 E1a region together with normal or mutant forms of the N-terminal half of the E1b region (HindIII G fragment) were generated by using a dominant selection marker, neo. Biochemically transformed cells containing a nonmutated HindIII G fragment proliferated more rapidly in Ca2+-deficient media, whereas cells containing a specific deletion within the E1b-encoded, 175-amino-acid (175R) (19-kilodalton) T-antigen gene and nontransformed cells grew at a slower rate. Furthermore, transformed cells that did not express the 175R T antigen and untransformed cells could not replicate their DNA efficiently in low-Ca2+ medium. Our results suggest that Ca2+ ions may provide an important stimulus for cell proliferation in adenovirus-transformed cells through a mechanism that involves the functions of the 175R T antigen.

Adenoviruses, Human↗
PubMed1992

A radiation-induced inhibitor of chromosome condensation and nuclear envelope breakdown in HeLa cells.

An in vitro microscopic assay for mitosis-inducing activity in mitotic HeLa cells was developed and used to demonstrate that cells irradiated and arrested in G2 phase of the cell cycle contain an inhibitor of mitosis. This assay system has a number of advantages over other assays including the use of autologous components (HeLa nuclei and mitotic cell extracts) in contrast to the microinjection method with Xenopus oocytes and without the requirements for microinjection expertise and Xenopus oocytes. The radiation-inducible inhibitor was detected at the lowest radiation dose tested (2 Gy) with maximal activity achieved within 30 min after radiation. Inhibitor activity decayed with time after radiation (2 Gy) with no activity detected at 6 h even though the cells remained in G2 phase, suggesting that either synthesis or activation of additional components is necessary for recovery from G2 arrest. The inhibitor activity was not detected in irradiated cells treated with caffeine to induce premature recovery from G2 arrest.

Animals↗
PubMed1987

The microtubule-organizing complex and the Golgi apparatus are co-localized around the entire nuclear envelope of interphase cardiac myocytes.

In most animal cells, the microtubule-organizing centre (MTOC) and the Golgi apparatus (GA) are co-localized on one side of the nucleus, an arrangement that allows these cells to acquire a functional polarity. An exception has been reported in the skeletal muscle myotube, where the MTOC and GA exhibit a circumnuclear distribution. We wished to determine if this unusual distribution of the MTOC and GA was peculiar to syncytial myotubes or reflected a pattern found in muscle cells generally. Immunofluorescence microscopic studies of cultured chicken skeletal muscle, cardiac muscle and gizzard smooth muscle cells were carried out using preimmune sera that recognized the pericentriolar material, anti-tubulin antibodies to label the MTOC, and fluorescent wheat-germ agglutinin to label the GA. These studies have shown that cardiac myocytes possess a circumnuclear distribution of their MTOC and GA as do skeletal myotubes, but smooth muscle cells exhibit the centrosomal MTOC and GA distribution found in most other cells. The circumnuclear MTOC/GA distribution therefore is associated with striated muscle cells. We also found that as embryonic cardiac myocytes pass through the cell cycle the microtubule-organizing activity in these cells switches from a circumnuclear distribution in interphase to the conventional centrosomal location during mitosis. Thus, cardiac myocytes provide a rare example of mononucleated animal cells that do not display a centrosomal MTOC or a polarized GA, and also reveal a system in which the MTOC structure can be reversibly altered in a cell cycle-dependent manner.

Animals↗
PubMed2004

beta-Catenin expression in thyroid follicular lesions: potential role in nuclear envelope changes in papillary carcinomas.

The morphologic distinction of benign and malignant thyroid follicular lesions can sometimes be challenging, therefore an immunohistochemical marker to aid in this distinction would be useful. beta-Catenin is one such potential marker. It is part of a membrane-bound cell growth-signaling complex that plays a role in cell adhesion, as well as in promotion of growth through activation of the Wnt signaling pathway. Oncogenic signaling occurs when beta-catenin is released, accumulates in the cytoplasm, translocates into the nucleus, and promotes transcription of genes including bcl-1 (cyclin D1) and c-myc that induce cell proliferation. Paraffin blocks from 133 thyroidectomy specimens were stained with monoclonal antibodies reactive with beta-catenin and cyclin D1. These included 53 cases of papillary thyroid carcinoma (PTC), 46 cases of follicular variant of papillary carcinoma (FVPC), 10 cases of follicular carcinoma (FC), and 24 cases of follicular adenoma (FA). Tissue from six normal thyroid specimens served as a control. The malignant lesions (PTC, FC, and FVPC) expressed strong cytoplasmic/nuclear staining and minimal residual membranous staining in 87%, 80%, and 71% of cases, respectively. In contrast, all normal thyroid tissue and 79% of FAs showed strong membranous reactivity with very minimal cytoplasmic staining. Interestingly, in 83% of PTC cases and 20% FVPCs, the intranuclear inclusions were distinctly beta-catenin positive. Cyclin D1 over expression correlated with cytoplasmic relocalization of beta-catenin in almost all cases, and no evidence of cyclin D1 gene amplification was observed. beta-Catenin can be of a diagnostic utility for thyroid lesions, because it highlights intranuclear inclusions in PTC, and shifts from a membranous localization to a cytoplasmic localization in malignant lesions. We speculate that the localization of beta-catenin in intranuclear inclusions may reflect a cytoskeletal remodeling activity of beta-catenin that is functionally significant for the PTC pathway.

Adenocarcinoma, Follicular↗
PubMed1992

Expression of nuclear envelope lamins A and C in human myeloid leukemias.

The lamins are intermediate filament proteins that form a fibrous layer at the periphery of the nucleus. Experiments in cell-free systems have suggested that mammalian lamins A and C mediate an interaction between chromatin and the inner nuclear membrane that is essential for the reformation of the nucleus after mitosis. Other investigations, however, have suggested that lamins A and C are absent from myeloid cells and myeloid leukemia cell lines. To further investigate this apparent paradox, highly sensitive Western blotting techniques were utilized in the present study to examine the expression of lamins A and C in a series of human myeloid leukemia cell lines and in bone marrow samples from patients with acute nonlymphocytic leukemia (ANLL) and chronic myelogenous leukemia. Western blotting revealed that HL-60 progranulocytic leukemia cells contained an average of 0.1 x 10(6) copies of lamins A and C per cell compared to 0.5 x 10(6) copies of lamin B1 (the quantitatively prominent human B-type lamin) per cell. During the process of phorbol ester-induced maturation to macrophages, the mRNA for lamins A and C increased in abundance, with a concomitant 4-fold increase in the average cellular content of these polypeptides. To rule out the possibility that the low but detectable levels of lamins A and C observed in untreated HL-60 cells reflected incipient maturation, the content of lamins A and C was analyzed in ANLL cell lines that do not mature toward granulocytes or monocytes. Lamins A and C were readily detected in cell lines (KG1a, HEL, Mo-7e) derived from patients with a variety of subtypes of ANLL. Expression of lamins A and C was not limited to myeloid cell lines. These polypeptides were also detectable in marrow samples from 9 of 26 patients with ANLL including at least 1 patient from each of the 5 subtypes of ANLL examined. In contrast, only 1 of 12 marrow samples from patients with aggressive phase chronic myelogenous leukemia and chronic myelogenous leukemia in blast crisis contained readily detectable lamins A and C. The implications of these findings for current hypotheses regarding the functions of the lamin polypeptides are discussed.

Blast Crisis↗