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Biomedical subjects

M M Portier

Publications and source records attributed to M M Portier.

At least 55 records · Page 3Linked to original sources
PubMed1987

Characterization of intermediate filaments expressed by Ewing tumor cell lines.

The histogenesis of Ewing sarcoma is still controversial; we therefore studied the expression of intermediate filaments (IF) in cell lines derived from Ewing tumors since identification of IF in tumor cells is considered a reliable marker of tissue origin and differentiation. All nine lines studied expressed vimentin IF; in addition, a small number of Ewing cells from three lines expressed keratin filaments. After treatment with phorbol esters, a high percentage of cells from these three lines synthesize keratin IF identified by immunoblotting as keratin 8 and 18 polypeptides, which are expressed by single epithelia and epithelial cells in early embryonic development. Furthermore cells from a fourth line synthesize keratins after transplantation in nude mice. These data indicate that, under certain conditions, undifferentiated Ewing cells may acquire an IF phenotype related to that of epithelial cells.

Animals↗
PubMed1986

Vimentin gene: expression in human lymphocytes and in Burkitt's lymphoma cells.

We have isolated a human genomic clone for the intermediate filament subunit vimentin with a DNA probe encoding chicken vimentin. We show that the gene for this protein exists as a single copy in the haploid human genome and is transcribed into one mature RNA species of 2 kb. In vitro translation of poly(A)+ mRNA in a rabbit reticulocyte cell-free system showed that vimentin is a major product of RNA from normal lymphocytes but not of RNA extracted from Burkitt cells. 2-kb vimentin mRNA can be detected with a DNA probe in normal lymphocytes and in fibroblasts, but not in cell lines derived from Burkitt's lymphoma (JI, JBL2, BJAB, DAUDI). The abundance of vimentin mRNA is correlated with the quantity of vimentin present in the cells, suggesting that the level of expression is regulated by the abundance of mRNA. The half-lives of vimentin mRNA were found identical in both fibroblasts and lymphocytes and belong to the class of stable mRNA.

Animals↗
PubMed1985

Monoclonal antibodies raised against Lewy bodies in brains from subjects with Parkinson's disease.

Monoclonal antibodies which immunocytochemically label Lewy bodies on sections of substantia nigra from subjects with Parkinson's disease were produced by immunization of mice with substantia nigra and locus coeruleus containing Lewy bodies from parkinsonian subjects post-mortem. Tests of specificity indicate that the antibodies do not recognize the same antigen. One of the antibodies (G7) immunocytochemically labels only Lewy bodies, the other (G9) also faintly labels the cell bodies of nigral dopaminergic neurons and cerebellar Purkinje cells in both normal and parkinsonian brains. Absorption experiments show, however, that the G7 antigen is present in normal substantia nigra and the G9 antigen in normal substantia nigra and Purkinje cells. Neither of the antibodies seems to be directed against neurofilament protein. Immunoblots after two-directional electrophoresis indicate that antibody G7 labels a protein with an iso-electric point around 5.6 and a mol. wt. of approximately 40 kdalton, whereas the protein labeled by antibody G9 has an iso-electric point of near 8 and a mol. wt. above 70 kdalton.

Antibodies, Monoclonal↗
PubMed1985

Expression of vimentin intermediate filament cytoskeleton in acute nonlymphoblastic leukemias.

Since vimentin intermediate filament (IF) expression in hemopoietic cells varies with the cell lineage as well as the state of differentiation of the cells, we studied the vimentin cytoskeleton by direct immunofluorescence and electron microscopy in 50 cases of acute nonlymphocytic leukemias. We found that malignant cells tend to reproduce the vimentin organization characteristic of their normal cellular counterpart. Thus, in M2 and M3 leukemias (French-American-British classification), vimentin was often reduced to a juxtanuclear bundle of filaments contrasting with the rich filamentous network expressed by M4 or M5 leukemias. In erythroblastic leukemias (M6) and megakaryoblastic leukemias, both identified by the expression of lineage-specific antigens, the absence of vimentin IFs could be correlated with the level of differentiation reached by the blasts. M1 leukemias displayed an abnormal pattern of vimentin organization with aggregated filaments giving a ring-like structure. However, no abnormality of the vimentin polypeptide could be detected by two-dimensional electrophoresis. These results show that the expression of the vimentin IF cytoskeleton may be a useful marker of differentiation in the study of leukemic cells.

Acute Disease↗
PubMed1984

Abnormal expression of vimentin intermediate filaments in human lymphoid cell lines with deletion or translocation of the distal end of chromosome 8.

The expression of vimentin, the major polypeptide of the intermediate filament (IFM) cytoskeleton of lymphoid cells, was studied in normal and malignant human lymphoid cell lines. Cells from 24 of 27 Burkitt's lymphoma cell lines (BLCL) were found to have an absent (16 lines) or decreased (8 lines) expression of vimentin IFM. In contrast, non-Burkitt's malignant lymphoid cell lines (5 lines) and lymphoblastoid cell lines (LCL) derived from normal B-cells (45 lines) exhibited a well-developed vimentin IFM network. However, low expression of vimentin was also found in 3 LCL derived from patients with the Langer-Giedion syndrome, which is characterized by a deletion of the distal end of chromosome 8. Treatment of vimentin-negative BLCL and Langer-Giedion LCL with azacytidine led to a transient reexpression of vimentin.

Azacitidine↗
PubMed1984

[Microheterogeneity of tubulin in the central nervous system of the quail (Coturnix coturnix japonica)].

Tubulin from the central nervous system of the Quail (Coturnix coturnix japonica) was analysed by two-dimensional gel electrophoresis. Either in soluble extracts or in tubulin enriched fractions, tubulin of forebrain, cerebellum and spinal cord is resolved into 3 components alpha, beta' and beta, characterized by their electrophoretic coordinates (alpha: pI = 5.4, MW = 54 kd, beta: pI = 5.2, MW = 52 kd; beta': pI = de mapping, by comparison with mouse brain alpha, beta and beta'-tubulin components. With highly resolutional isoelectric focusing 6 alpha isotubulins and 14 beta isotubulins are found in enriched-tubulin fractions of Quail forebrain and cerebellum.

Animals↗
PubMed1982

Changes in some cytoskeletal proteins during neuroblastoma cell differentiation.

After in vitro microtubule assembly of mouse neuroblastoma crude extracts, six protein species migrate in the tubulin region of two-dimensional electrophoregrams. The evolution of these forms after morphological cell differentiation of the clone NIE115 shows two major modifications. Form 5 decreased drastically while form 6 increases during neurite formation. Peptide mapping analysis reveals that forms 5 and 6 are vimentin, a component of intermediate filaments, and beta-tubulin subunit, respectively. Sodium butyrate treatment of NIE115 cells or serum starvation of NIA103 cells, conditions blocking cell division and failing to induce morphological differentiation, prevent any modifications in the relative proportion of these proteins. It is concluded that the changes in the distribution of the tubulin isoforms and vimentin are directly related to neurite formation.

Animals↗
PubMed1980

Identification of rat brain polysomes synthesizing the brain specific enolase (14.3.2 protein), S100 protein and alpha and beta tubulin subunits.

Polysomes prepared from frozen rat brain powder were fractionated by centrifugation in a sucrose gradient. Individual fractions were used to program a reticulocyte lysate in a run-off reaction. The products of cell-free synthesis were assayed for the brain-specific enolase (14.3.2 protein) and S100 protein by immunoprecipitation with specific antisera and for tubulin by two-dimensional electrophoresis in polyacrylamide slab gels. The relative synthesis of these proteins by unfractionated free brain polysomes were 0.1 per cent, 0.05 per cent and 0.7 per cent respectively. After centrifugation in a sucrose gradient polysomes synthesizing S100 protein were separated from those synthesizing the other two markers. There was a threefold enrichment in the specific messenger RNA activity for each of the three proteins studied in their respective peak fractions of polysomes.

Animals↗
PubMed1980

Partial purification of the alpha-tubulin and beta-tubulin messenger RNAs from rat brain.

Poly(A)-containing RNA from frozen adult rat brain were fractionated by centrifugation in a formamide/sucrose gradient. Individual fractions were used to program protein synthesis in vitro in a reticulocyte lysate. The cell-free translation products were analyzed by two-dimensional electrophoresis in polyacrylamide slab gels. We observed a heterodispersion of the mRNA translation activity coding for the beta-tubulin subunit which contrasts with a relatively homogeneous distribution of the alpha-tubulin subunit mRNA. These last mRNA species are present in a peak which sediments near the 18-S region of the gradient whereas the beta-tubulin mRNA activity is predominant in the fractions corresponding to the heaviest mRNA species. When these heaviest RNAs were separated again by centrifugation in a second formamide/sucrose gradient, a poly(A)-rich RNA population was obtained that was enriched in RNA for programming the beta-tubulin subunit. Analysis of the products whose synthesis in vitro was directed by this mRNA population revealed that beta tubulin was the main protein formed, the ratio beta/alpha being more than tenfold greater than in the products translated in vitro using total poly(A)-rich RNA.

Animals↗
PubMed1979

Translation in vitro of Tetrahymena pyriformis polyadenylated mRNA. Identification of tubulin amongst the translated products and demonstration of its heterogeneity.

The capacity of poly(A)-containing RNA of the protozoan ciliate Tetrahymena pyriformis to direct the synthesis of proteins in vitro has been tested using two cell-free systems: a wheat germ extract and a rabbit reticulocyte lysate. The results obtained with these two systems are compared and the identification of alpha and beta tubulins among the products of protein synthesis in vitro, after separation by one-dimensional and two-dimensional electrophoresis, is described. By isoelectric focusing in polyacrylamide gels, each species of tubulin is resolved into several bands, suggesting that the main subunits are more heterogeneous than has been generally described. Poly(A)-containing RNA has also been fractionated on a 70% formamide/sucrose gradient and it is shown that alpha and beta tubulins are coded by separate mRNAs.

Animals↗
PubMed1977

RNA polysomes and RNA synthesis in the silk glands of the silkworm Bombyx mori;.

Total RNA polymerase activity, as well as the proportion of alpha-amantin-sensitive and resistant during activity, have been measured in the posterior silk glands of the silkworm as a function of growth the fifth larval instar. During the first 5 days, termed the growth phase, the total enzyme activity and particularly the portion that is alpha-amantin-resistant increases to reach a peak value and thereafter declines during the secretory phase, Much of the enzyme remains firmly bound and insoluble. Heparin only only does not inhibit this insoluble and probably chromatin-bound activity which would indicate lack of initiation, but it enhances the activity. A large proportion of newly transcribed RNA is released from the transcription complex. The synthesis of RNA has been studied both qualitatively and quantitatively during the same period. RNA synthesis becomes important on the second day of the fifth instar, as does the RNA polymerase, and stays at a high level for several more days. The results from these studied as well as those with incorporation of 32P indicate interference of varying precursor pools in quantitatively measured RNA synthesis. However, RNA content as well as RNA synthesis in vitro show a close correlation with RNA polymerase activity. The labeled RNAs extracted at different days of the fifth instar have been fractioned on sucrose gradients; this demonstrated that the predominant product of RNA synthesis, as followed by [3H]uridine incorporation at short time intervals, is 45-S preribosomal RNA and 4-5 S RNA. The 45-S RNA is transformed to 19-S and 30-S ribosomal RNA as time progresses or after a chase with unlabeled and/or actinomycin D. There also exists a component heavier than 45S which is fairly rapidly labeled to a small extent.

Amanitins↗