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G Buttin

Publications and source records attributed to G Buttin.

At least 73 records · Page 4Linked to original sources
PubMed1981

Cross-linking of surface immunoglobulins and endocytosis of antigen are not sufficient to suppress antibody production of two hybridoma cell lines.

The two cell lines Lev 1-3 and AS3, which secrete monoclonal anti-levan antibody and express surface membrane immunoglobulins that are capable of binding the levan, were cultured for 24 h or 48 h with levan of various molecular weights (5 x 10(4), 2 x 10(5) or 2 x 10(7) daltons). The production of antibody was measured by a plaque-forming cell assay for AS3 cells and by biosynthetic labelling for Lev 1-3 cells. Surface immunoglobulins were detected by a rosette-forming cell assay. By using immunoenzymatic procedures, we observed that levan of 5 x 10(4) and 2 x 10(5) daltons was intensely endocytosed by the cells and localized mainly in the cellular center, whereas levan of 2 x 10(7) daltons remained mostly associated with the plasma membrane and formed surface aggregates. After transfer of cells in levan-free medium, it was shown that internalized levan could persist several days inside the cells without being degraded. Viability, growth, antibody synthesis and secretion were not modified in cells cultured with levan, whatever the molecular weight of the antigen used. Our results show that cross-linking of surface immunoglobulins by multivalent antigen or endocytosis of antigen do not appear to be sufficient to induce a suppression of antibody production or membrane immunoglobulin expression.

Animals↗
PubMed1980

Idiotypic network: the MOPC 460 system.

The results presented in this communication show very clearly that the mice with IghCa haplotype can produce anti-TNP antibodies from which a fraction share the idiotypic determinants expressed on M460 myeloma protein. Nevertheless the gene(s) which encode(s) this specificity, is present in the repertoire of strains of mice which have not this haplotype. As in DBA/2 mice this silent clone(s) can be stimulated by an appropriate immunological manipulation and their progeny even can be frozen in hybridomas. The expression of 460 Id positive anti-TNP antibody forming cells is regulated by T cells in BALB/c mice. These T cells are specific for 460 Id and share the idiotypic determinants of anti-460 Id antibodies since they were not found in BALB/c mice with an Ab3 type of response.

Animals↗
PubMed1979

Anti-peroxidase antibody-secreting hybrid lines. I. Identification, cloning and cell characterization.

Anti-peroxidase antibody (Ab)-secreting hybrids have been produced by fusion of peroxidase (PO)-immunized mouse lymph node cells and immunoglobulin (Ig)-secreting P3-X63-Ag8 (X63) myeloma cells. Identification of Ab-secreting hybrids can be performed as early as day 5 after cell fusion by the hemolytic plaque assay. Immediately after identification, hybrids were directly isolated, by means of a micropipette, into Terasaki microchambers containing nutrient medium and a thymocyte filler layer. The yield of secreting hybrids is improved by using this procedure. All the cells of the PO 772 C2 clone show the same ultrastructural pattern and immunocytological properties; they are proplasmocytes, as are the parental X63 cells; they present intracisternae Ab and show no Ig or Fc receptors at the cell surface. Over 90% of viable PO 772 C2 cells form specific plaques. Isoelectric focusing and sodium dodecyl sulfate polyacrylamide gel electrophoresis show that the cells of this clone secrete Ab; the secreted Ig are formed with chi and gamma 1 chains from the parental X63 cells and specific L and H chains from the lymphoid parent. These biological investigations demonstrate the relative stability of the PO 772 C2 clone secreting anti-peroxidase antibody.

Animals↗
PubMed1979

Studies on 1-beta-D-arabinofuranosyl cytosine-resistant mutants of Chinese hamster fibroblasts: III. Joint resistance to arabinofuranosyl cytosine and to excess thymidine--a semidominant manifestation of deoxycytidine triphosphate pool expansion.

Variants isolated from mutagenized Chinese hamster fibroblasts by a single cycle of exposure to ara-C distributed into two classes: (1) deoxycytidine (dC) kinase deficient clones with a high level of resistance, this phenotype was recessive in hybrids; and (2) clones exhibiting joint resistance to thymidine (dT) and to "low" ara-C concentration, this phenotype was accounted for by an increased dCTP pool. The incorporation of exogenous dC into macromolecules was markedly altered in these variants. In hybrids, the phenotype of joint resistance to dT and ara-C was semidominant. Through a second selection step, variants cumulating recessive high resistance to ara-C and semidominant dT resistance were recovered. The identification of these two classes of ara-C-resistant variants suggests an interpretation of the known phenotypes of ara-C resistance as manifestations of chromosomal gene mutations. Dominant resistance mutations might contribute to the survival of cancer cells during prolonged ara-C chemotherapy.

Animals↗
PubMed1979

A new rapid rosette-forming cell micromethod for the detection of antibody-synthesizing hybridomas.

The method reported here describes a microrosetting assay which allows the early detection of antibody-synthesizing hybridomas. This method is specific, requires very few hybridoma cells and avoids artifacts resulting from the presence of antibodies secreted by spleen cells in the primary hybridoma cultures. It is easy to perform and allows the screening of more than one hundred independent clones within a few hours.

Animals↗
PubMed1979

Differential staining and segregation of parental chromosomes in mouse-rabbit hybridomas.

Hoechst 33258 fluorescent staining can be coupled with G-banding to identify the chromosomal contribution of each parent in mouse-rabbit hybridomas. A fast and essentially complete segregation of rabbit chromosomes is obtained in these cells. The rabbit X chromosome is preferentially maintained in media imposing HGPRT activity for cell growth. Mouse-rabbit hybridomas, some of which secrete rabbit immunoglobulin chains, should be a convenient material for the identification of chromosomes governing rabbit Ig chain synthesis.

Animals↗
PubMed1978

Aanlysis of dCMP deaminase and CDP reductase levels in hamster cells infected by herpes simplex virus.

Several enzymatic activities involved in the biosynthetic pathways of nucleotides, including thymidine kinase, which has been used as a biochemical marker in studies of gene transfer, are induced by herpes simplex virus (HSV). The utility of additional markers prompted us to reanalyze the effects of HSV infection on the activities of two other enzymes for which direct selective methods can be devised: dCMP deaminase and CDP reductase. For this purpose, mutant Chinese hamster (lA1) cells devoid of dCMP deaminase activity or Syrian hamster (BHK-21/C13) cells were infected by HSV type 1 or 2, and the activities of thymidine kinase, dCMP deaminase, and CDP reductase were measured in the cell extracts. The reported induction of thymidine kinase and CDP reductase by HSV was confirmed, whereas the stimulation of dCMP deaminase activity could not be observed. For both cell lines, the HSV-induced CDP reductase differed from the host enzyme by sensitivity to inhibition by both dTTP and dATP. This property should be helpful in developing a selection system for this activity.

Animals↗
PubMed1977

The control of cell proliferation by preformed purines: a genetic study. I. Isolation and preliminary characterization of Chinese hamster lines with single or multiple defects in purine "salvage" pathways.

Sublines with single or multiple defects in purine "salvage" enzymes were isolated from the Chinese hamster fibroblastic line GMA32 through single or successive one-step selections for resistance to purine analogs. They were examined for their ability to incorporate purine bases and nucleosides into macromolecules, for their sensitivity to growth inhibitory purines, and for their rescue by exogenous purines from deprivation imposed by metabolic inhibitors of endogenous synthesis. The results show that a deficiency of either adenosine kinase (EC 2.7.1.20), adenine phosphoribosyltransferase (EC 2.4.2.7) or hypoxanthine guanine phosphoribosyltransferase (EC 2.4.2.8) abolishes the ability of adenine to cause cell death by interfering with pyrimidine synthesis; on the other hand, the pyrimidine starvation caused by adenosine is fully prevented only by a deficiency of adenosine kinase.

Adenine Phosphoribosyltransferase↗
PubMed1977

The control of cell proliferation by preformed purines: a genetic study. II. Pleiotropic manifestations and mechanism of a control exerted by adenylic purines on PRPP synthesis.

When plated in medium containing 0.5 microgram/ml coformycin and adenosine (or adenine) fibroblasts were killed, even if pyrimidines were supplied. Measurements of N-formylglycine amide ribonucleotide synthesis showed that lethality is a manifestation of purine starvation. In the case of adenosine kinase deficient cells, growth was restored by hypoxanthine. The adenylic derivatives block only purine biosynthesis, presumably by inhibition of PRPP-amidotransferase. In this same medium, wild-type cells exhibited symptoms of PRPP deprivation: purine and pyrimidine syntheses were both shut off and HGPRT was simultaneously inactivated. The pleiotropic control by adenosine was abolished in adenosine-resistant mutants that behaved as PRPP "over-producers." These mutations conferred partial resistance to various toxic purine and pyrimidine analogs and preserved HGPRT activity in adenosine-containing medium. This permits selection against these mutants. Evidence suggesting that adenosine kinase products may fulfill a specific function in the regulation of PRPP synthesis is discussed.

Adenine↗
PubMed1975

Prophage induction and cell division in E. coli. III. Mutations sfiA and sfiB restore division in tif and lon strains and permit the expression of mutator properties of tif.

In E. coli K12, cell filamentation promoted by tif is enhanced by the lon mutation; in contrast, prophage induction and repair of UV-irradiated phage lambda, also promoted by tif, are not affected by lon. From a tif lon double mutant, "revertants" having recovered the ability to divide at 41 degrees were isolated, among which most (95%) had also lost their Lon filamentous phenotype after ultraviolet (UV) irradiation. From these 95% of revertants: (1) 94% are suppressed for the whole Tif phenotype, by additional mutations that render them deficient in DNA repair, as judged from their high UV sensitivity; some have been characterized as recA mutants. (2) 1% have recovered a control on cell division at 41 degrees or after UV irradiation by means of secondary mutations altering neither the other phenotypic properties of tif and lon, nor the repair and recombination ability of the cells: in particular, this class of "revertants" remains thermoinducible upon lysogenisation; the mutations which specifically suppress filamentation have been mapped at two loci, sfiA and sfiB, cotransducible respectively with pyrD and leu. In the remaining 5% of revertants that still exhibit an UV-induced filamentous growth, 3% can be tentatively classified as true tif+ revertants; 2% behave as tif thermodependent revertants, showing suppression of the Tif (and Lon) phenotype only at 41 degrees: 2recAts have been identified in this class. Non-lysogenic tif lon sfi and tif sfi strains remain viable during prolonged growth at 41 degrees. Under these conditions, tif expresses mutator properties, which can be conveniently analyzed in this sfi background. The action of lif, lon and sfi mutations is tentatively interpreted on the basis of a negative control of cell division specifically associated with DNA repair.

Cell Division↗
PubMed1975

Temperature-sensitive cell cycle mutants: a chinese hamster cell line with a reversible block in cytokinesis.

A thermosensitive line (TS 111) was isolated from a suspension culture of Chinese hamster fibroblasts, using a BUdR suicide selection technique. In this line, cytokinesis is blocked at 39 degrees C. DNA and protein synthesis are not arrested but keep on at a steady rate. Giant cells are produced which accumulate either numerous nuclei or one big nucleus with several nucleoli and more than a hundred chromosomes. At each nuclear cycle, all the chromosomes in the cell appear to condense in a synchronous manner, although it is possible that not all the sets of chromosomes duplicate. When the culture is returned to the permissive temperature (34 degrees C) after a prolonged arrest at the restrictive temperature, cytokinesis resumes with early extrusion of karyoplasts from multinucleated cells. The division block is independent of cell density in suspension culture and is not prevented by cell contact when cells grow attached to Petri dishes. At 34 degrees C, a residual expression of the mutation is indicated by the presence of binucleate and up to 30% anucleate cells. A remarkable similarity and some synergism exists between the mutation and cytochalasin B effects.

Animals↗