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M Schena

Publications and source records attributed to M Schena.

At least 55 records · Page 3Linked to original sources
PubMed1991

Expression of the c-myc protein is down-regulated at the terminal stages during in vitro differentiation of B-type chronic lymphocytic leukemia cells.

The translocated c-myc oncogene in Burkitt's lymphoma (BL) and murine plasmacytoma (MPC) has been proposed to be expressed at a stage of differentiation at which the gene is normally silent, resulting in a continuous proliferation and an inhibited terminal differentiation. To determine whether c-myc is differently expressed at the various stages of the differentiation pathway, we used B-type chronic lymphocytic leukemia (B-CLL) cells, representing resting B lymphocytes, inducible to proliferation and/or differentiation in vitro. The c-myc protein, and Ig lambda-light chain and PCA-1 antigen as markers of B-cell maturation, were analyzed in single, morphologically defined cells by immunocytochemical double-staining. The proliferation of individual cells was determined by 3H-thymidine incorporation and by analysis of Ki-67 antigen expression. The results show that the level of c-myc expression correlates to the stage of differentiation and to the proliferative activity. Uninduced resting cells did not express c-myc. The c-myc protein was observed in the highest amount at the proliferative B-lymphoblast stage of maturation and was reduced in plasmablasts and undetectable in plasma cells. The results suggest that maturation of B cells into nonproliferative, terminally differentiated plasma cells is associated with a downregulated c-myc expression and thus support the view that the deregulated c-myc gene in BL and MPC is expressed at an inappropriate stage of maturation and thereby inhibits terminal differentiation.

Antigens, Surface↗
PubMed1990

An inducible expression vector for both fission and budding yeast.

We have developed a vector system for inducible gene expression in both fission yeast (Schizosaccharomyces pombe) and budding yeast (Saccharomyces cerevisiae). The autonomously replicating expression vector contains multiple glucocorticoid response elements, rendering a linked promoter inducible 20-70-fold by glucocorticoid hormones in the presence of the mammalian glucocorticoid receptor. A polylinker with several unique cloning sites allows insertion of cDNAs of interest. Glucocorticoids are gratuitous signalling molecules in yeast, exerting little or no effect on the expression of genes other than those fused to the regulated promoter.

Base Sequence↗
PubMed1990

Integrin distribution and cytoskeleton organization in normal and malignant monocytes.

In this work we have mapped by double-label immunofluorescence the cellular distribution of integrins and their relationship with cytoskeletal proteins in normal and malignant monocytes. In normal monocytes, CD18 and CD11c are concentrated at specific adhesion sites, named podosomes, together with actin, vinculin, and talin, while CD11a, CD11b, CD29/beta 1, CDw49d/alpha 4 and CD54/ICAM-1 retain a diffuse distribution on the cell surface without a selective pattern of localization. U-937 and fresh leukemic monoblasts under standard culture conditions do not adhere and do not form podosomes, but, when treated with TPA, they promptly adhere to substrate, form podosomes and focal adhesions in different cells and display the same integrin/cytoskeleton relationship as normal mature monocytes. Further, in these cells CD18, CD11a, CD11c, ICAM-1, and talin, but not vinculin, co-localize in homotypic cell junctions, thus showing a close relationship between integrins and talin. These observations provide morphological evidence that, in cells of the monocytic lineage, podosome formation is acquired upon differentiation and different integrins are selectively localized at different adhesion sites.

CD18 Antigens↗
PubMed1989

The evolutionary conservation of eukaryotic gene transcription.

The basic components required for eukaryotic gene transcription have been highly conserved in evolution. Structural and functional homology has now been documented among promoters, promoter factors, regulatory proteins, and RNA polymerases from eukaryotes as diverse as yeast and mammals. The ability of these proteins and DNA sequences to function across phylogenetic boundaries demonstrates that common molecular mechanisms underlie gene control in all eukaryotic cells, and provides the basis for powerful new approaches to the study of eukaryotic gene transcription.

Animals↗
PubMed1989

Interleukin 3 and interleukin 6 synergistically promote the proliferation and differentiation of malignant plasma cell precursors in multiple myeloma.

PBMC from 11 patients with multiple myeloma (MM) were cultured in vitro in presence of IL-3 and IL-6. After 3 d, actively proliferating immunoblast-like B cells (20-62%) were apparent. After 6 d, a population of morphologically evident plasma cells was observed (30-50%) that expressed, in each individual case, the same light and heavy chain produced by bone marrow malignant plasma cells. We conclude that in MM the malignant plasma cell precursors are circulating and their growth and terminal differentiation are under the synergistic control of IL-3 and IL-6.

Cell Differentiation↗
PubMed1989

Na+/H+ exchange activation mediates the lipopolysaccharide-induced proliferation of human B lymphocytes and is impaired in malignant B-chronic lymphocytic leukemia lymphocytes.

In various mammalian cell types the stimulation of the plasma membrane amiloride-sensitive Na+/H+ exchange and the resulting increase of intracellular pH (pHi) play a key role in the initiation of cell proliferation. In the present work we have investigated whether Na+/H+ exchange is involved in normal human B cell proliferation and whether it is also operating in malignant B-chronic lymphocytic leukemia (B-CLL) lymphocytes. Our results show that: 1) normal human B cells contain an operating Na+/H+ exchanger, as inferred by their ability to recover pHi after acid-loading in a HCO3- -free medium and by evidences that LPS and phorbol ester PMA elicit a pHi rise inhibitable by either 5-(N-ethyl-N-isopropyl)amiloride (EIPA) or a Na+-free medium; 2) LPS-induced proliferation of normal human B cells is strongly inhibited when the amiloride analog EIPA (5 microM) is present in the culture medium (after 72 h the proportion of B cells incorporation bromodeoxyuridine falls from 13.9 +/- 3.9% to 2.8 +/- 1.1%); 3) EIPA does not affect BdR incorporation when B cells proliferation is induced by the co-mitogenic activity of IL-4 and low m.w. B cell growth factor (BCGF); 4) B-CLL cells, which proliferate in response to IL-4/BCGF but not to LPS, fail to increase pHi above their pHi resting levels when challenged with LPS or PMA and pHi recovery after acid-loading is highly impaired. These results lead to conclude that Na+/H+ exchange operation is necessary for LPS-(but not for IL-4/BCGF)-induced proliferation of human normal B lymphocytes and that Na+/H+ exchange activation is impaired in malignant B-CLL lymphocytes.

Aged↗
PubMed1989

Mutations in the glucocorticoid receptor zinc finger region that distinguish interdigitated DNA binding and transcriptional enhancement activities.

Mammalian glucocorticoid receptors bind specifically to glucocorticoid response element (GRE) DNA sequences and enhance transcription from GRE-linked promoters in mammalian cells and in yeast. We randomly mutagenized a segment of the receptor encompassing sequences responsible for DNA-binding and transcriptional regulation and screened in yeast for receptor defects. The mutations all mapped to a 66-amino-acid subregion that includes two zinc fingers; in general parallel phenotypes were observed in yeast and animal cells. Mutants defective for DNA binding also failed either to enhance or to repress transcription. However, several mutations in the second finger selectively impaired enhancement; we suggest that such 'positive control' mutants may alter protein-protein contacts required for transcriptional activation.

DNA↗
PubMed1989

Circulating malignant precursors in monoclonal gammopathies.

Peripheral blood mononuclear cells (PBMC) from 14 patients with multiple myeloma (MM), 3 patients with benign monoclonal gammopathy, 3 patients with Waldenstrom's macroglobulinaemia (WM) and 2 patients with B-cell chronic lymphocytic leukemia (B-CLL) were cultured in vitro in the presence of IL-3 and IL-6. After 3 days, actively proliferating immunoblast-like B cells were apparent in 12/14 cases of MM, 0/3 BMG, 3/3 WM and 0/2 B-CLL. After 6 d, B blasts had evolved into morphologically evident plasma cells expressing the specific monoclonal light and heavy chains. The data indicate that the concerted action of IL-3 and IL-6 synergistically promotes the proliferation and differentiation of circulating plasmacell precursors in malignant monoclonal gammopathies.

Cell Differentiation↗
PubMed1989

Kinetics of human hemopoietic cells after in vivo administration of granulocyte-macrophage colony-stimulating factor.

The kinetic changes induced by granulocyte-macrophage colony-stimulating factor (GM-CSF) on hemopoietic cells were assessed in physiological conditions by administering GM-CSF (8 micrograms/kg per d) for 3 d to nine patients with solid tumors and normal bone marrow (BM), before chemotherapy. GM-CSF increased the number of circulating granulocytes and monocytes; platelets, erythrocytes, lymphocyte number, and subsets were unmodified. GM-CSF increased the percentage of BM S phase BFU-E (from 32 +/- 7 to 79 +/- 16%), day 14 colony-forming unit granulocyte-macrophage (CFU-GM) (from 43 +/- 20 to 82 +/- 11%) and day 7 CFU-GM (from 41 +/- 14 to 56 +/- 20%). The percentage of BM myeloblasts, promyelocytes, and myelocytes in S phase increased from 26 +/- 14 to 41 +/- 6%, and that of erythroblasts increased from 25 +/- 12 to 30 +/- 12%. This suggests that GM-CSF activates both erythroid and granulomonopoietic progenitors but that, among the morphologically recognizable BM precursors, only the granulomonopoietic lineage is a direct target of the molecule. GM-CSF increased the birth rate of cycling cells from 1.3 to 3.4 cells %/h and decreased the duration of the S phase from 14.3 to 9.1 h and the cell cycle time from 86 to 26 h. After treatment discontinuation, the number of circulating granulocytes and monocytes rapidly fell. The proportion of S phase BM cells dropped to values lower than pretreatment levels, suggesting a period of relative refractoriness to cell cycle-active antineoplastic agents.

Bone Marrow↗
PubMed1989

Human normal CD5+ B lymphocytes can be induced to differentiate to CD5- B lymphocytes with germinal center cell features.

A significant proportion of cord blood CD5+ B cells express the activation molecules CD23, CD25, and transferrin receptor; react with the cell-cycle-associated monoclonal antibody (MoAb) Ki67; can be induced to enter the S phase of cell cycle by interleukin-2 (IL-2), IL-4, or low-molecular-weight B-cell growth factor (Imw-BCGF) and, exposed to IL-1 and IL-2, acquire the features (sIgD-, CD5-, CD10+, CD38+) of B blasts proliferating in the germinal centers of secondary follicles. These findings indicate that CD5+ B cells are preactivated and, in the proper microenvironment, may give rise to CD5- B cells.

Animals↗
PubMed1988

Mammalian glucocorticoid receptor derivatives enhance transcription in yeast.

In mammalian cells, the glucocorticoid receptor binds specifically to glucocorticoid response element (GRE) DNA sequences and enhances transcription from linked promoters. It is shown here that derivatives of the glucocorticoid receptor also enhance transcription when expressed in yeast. Receptor-mediated enhancement in yeast was observed in fusions of GRE sequences to the yeast cytochrome c1 (CYC1) promoter; the CYC1 upstream activator sequences were not essential, since enhancement was observed in fusions of GREs to mutant CYC1 promoters retaining only the TATA region and transcription startpoints. It is concluded that the receptor operates by a common, highly conserved mechanism in yeast and mammalian cells.

Animals↗
PubMed1988

CD5 and CD21 molecules are a functional unit in the cell/substrate adhesion of B-chronic lymphocytic leukemia cells.

The modulation of surface molecules on B-chronic lymphocytic leukemia (B-CLL) cells was studied in vitro by incubation with CD19, CD20, CD21, CD5 and anti-IgM antibodies. The cytoplasmic changes were evaluated by analyzing the organization of cytoskeletal F-actin and the adhesive properties of stimulated B-CLL cells. The following observations were made: (a) CD5 antigen is capped on the surface of B-CLL cells (but not on normal CD5+ B and T lymphocytes). (b) On B-CLL cells, CD5 and CD21, the receptors for the C3d fraction of complement, co-cap and co-modulate while surface IgM as well as CD19 and CD20 do not cap. (c) B-CLL cells, after capping of CD5 or CD21 surface molecules, fail to organize F-actin into podosomes. (d) The pre-incubation of B-CLL cells with either CD5 or CD21 antibodies prevents their binding to purified C3d protein used to coat coverslips. These data indicate that an intimate spatial relationship exists between CD5 and CD21 molecules on the B-CLL surface. The CD5-CD21 complex is involved in the redistribution of cytoskeletal proteins which may control the adhesive properties of these malignant B cells.

Actins↗
PubMed1988

Noninvasive assessment of pulmonary hypertension: a simultaneous echo-Doppler hemodynamic study.

Thirty patients with stable chronic obstructive lung disease (COLD) underwent an echo-Doppler examination before and during right heart catheterization. No statistically significant differences between observations for any of two-dimensional echo-Doppler parameters were found. The measurement of all parameters taken during the catheterization correlated better with mean pulmonary artery pressure (mPAP) than those taken before. This difference was most evident for the isovolumetric acceleration time (r = 0.71 before versus r = 0.85 during the catheterization) and relaxation time (r = -0.75 before versus r = -0.87 during the catheterization). The multiple correlation coefficient for all measured parameters and mPAP was 0.83 before and 0.92 during the catheterization. In conclusion, in patients with COLD, it appears possible to get reliable information about PAP using noninvasive techniques.

Adult↗
PubMed1988

Vinculin, talin, and integrins are localized at specific adhesion sites of malignant B lymphocytes.

The microanatomy of the dot-shaped, close-contact sites called podosomes and the mechanism of their formation have been investigated in vitro in the malignant lymphocytes of B chronic lymphocytic leukemia (B-CLL). In this paper the authors demonstrate that in B-CLL podosomes: (1) vinculin, talin, and beta 2 integrin (CD18) rings surround an F-actin core; (2) the beta 1 integrin is localized within the F-actin core; (3) the beta 3 integrin is not present. This distribution and organization of adhesion-related molecules appears to be unique to B-CLL lymphocytes, since it has not been observed in normal B cells. B-CLL adhesion and podosome formation are inhibited by the synthetic peptide GRGDSP that contains the Arg-Gly-Asp (RGD) sequence.

Amino Acid Sequence↗