Search PubMed⌕ Search

Biomedical subjects

G Torpier

Publications and source records attributed to G Torpier.

At least 91 records · Page 5Linked to original sources
PubMed1979

In vitro killing of S. mansoni schistosomula by eosinophils from infected rats: role of cytophilic antibodies.

The cytotoxic effect of peritoneal cells from Schistosoma mansoni-infected rats against antibody-opsonized or nonopsonized schistosomula in vitro has been studied during the course of infection. Eosinophil-enriched cell preparations were shown to have a high cytotoxic effect on schistosomula in the absence of antibody. The killer cells were identified as eosinophils. As in the ADCC mechanism previously described, mast cell-eosinophil interaction was required for eosinophil cytotoxicity. Rosette formation using S. mansoni antigen-coated erythrocytes was used to demonstrate the presence of anti-S. mansoni IgG2a antibody at the surface of infected eosinophils. Passive sensitization of normal eosinophils with ultracentrifugation pellets of immune rat serum resulted in a significant cytotoxicity of sensitized eosinophils. A close relationship was found between the cytotoxic activity of infected cells and the ability of the corresponding infected serum to arm normal eosinophils. At certain periods after infection, eosinophils from infected rats were less effective than normal eosinophils on antibody-coated schistosomula. EA- (rat) rosetting assay and blockade experiments with homologous immune complexes have revealed in a kinetic study that the blocking of cytotoxic activity of infected eosinophils was related to heat-stable circulating immune complexes. The possible role of immune complexes either in arming or inhibiting effector cells is suggested.

Animals↗
PubMed1978

Eosinophil-dependent cytotoxicity in rat schistosomiasis. Involvement of IgG2a antibody and role of mast cells.

Using Schistoma mansoni schistosomula collected in vitro and sensitized with 42-day-infected rat serum, normal rat peritoneal cells enriched in eosinophils were proven to subsequently adhere to and kill the schistosomula within 24 to 48 h. The cell-dependent, heat-stable antibody in infected rat serum reached a peak between 30 and 42 days after infection. Inhibition experiments with aggregated immunoglobulins indicated the role of IgG2a antibody in the adherence of eosinophils to sensitized schistosomula. The immune absorption technique showed that IgG2a antibody was involved in the mechanism of cytotoxicity of effector to target cells, whereas the role of IgE antibody could be excluded. Ultrastructural studies revealed the constant presence of eosinophils and mast cells in contact with schistosomula. The use of purified cell populations showed that the cytotoxic effect of the original cell population was significantly decreased after depletion of mast cells and partially restored after addition of mast cells. These observations, together with those concerning the role of IgE immune complexes in macrophage cytotoxicity, suggest the possible participation of anaphylactic antibodies in immunity to schistosomes in the rat.

Animals↗
PubMed1978

Adenovirus type 2 assembly analyzed by reversible cross-linking of labile intermediates.

Dimethyl-4,4'-dithiobisbutyrimidate dihydrochloride was used as a cleavable cross-linking reagent to maintain the structure of labile intermediates in adenovirus type 2 assembly. Analysis on sucrose gradients of nuclear adenovirus particles revealed two size classes, with sedimentation rates of 750 and 600S. After reversible fixation with diimido ester, the different classes were further separated on CsCl gradients and characterized with regard to their buoyant density, DNA content, and polypeptide composition. The 750S particles banded at 1.345 g/cm3 in CsCl, contained a DNA with a sedimentation coefficient of 34S in alkaline sucrose gradients, and had a polypeptide composition similar to that of young virions. The 600S population consisted of two types of particles with buoyant densities of 1.315 and 1.37 g/cm3. The 1.315-g/cm3 particles contained a DNA fragment of 7--11S and lacked the core proteins V and VII. In their place were found precursors P VI and P VIII and two nonvirion proteins with molecular weights of 50,000 (50K) and 39,000 (39K). 34S DNA was present in the 1.37-g/cm3 particles, which also lacked core proteins V and VII, as well as the 50K and 39K. Pulse-chase labeling kinetics suggested that the 1.315-g/cm3 particles were anterior to the 1.37-g/cm3 particles, themselves preceding the 1.345-g/cm3 young virions, and that the release of both 50K and 39K, possible scaffolding proteins, was required for entry of viral DNA.

Adenoviruses, Human↗
PubMed1977

[Freeze fracture study of Toxoplasma and Sarcocystis infective stages (author's transl)].

Infective stages of Toxoplasma and Sarcocystis have been studied by the freeze fracture technique. The outer membrane of the pellicle is continuous and shows an apical 8 + 1 particles rosette in the P fracture face. The inner membrane complex is made of rectangular flattened vesicles aligned in longitudinal rows and joined in a puzzle like fashion. Sarcocystis has 11 of these rows whereas their number varies in Toxoplasma. A posterior interruption is present. Anteriorly is one truncated conical plate apically opened by a vertical ridge. The membranes of the inner complex are characterized by parallel alignment of particles (in P faces) some of which are joined and continuous with double rows radiating in the apical cap. Those rows correspond in number and arrangement with the underlying microtubules. The rhoptries membranes show periodic circular arrays of particles.

Animals↗
PubMed1975

XC-cell fusion induced by murine plasmocytoma cells. II. Cytological and ultrastructural study.

The MF2 strain, a mouse myeloma derived cell line, was found to induce the mixed culture cytopathogenicity test when cocultured with XC cells. Only one MF2 cell was present per syncytium, as shown by autoradiography. Pretreatment of cells with inhibitors of DNA, RNA or protein synthesis suggested that a normal RNA synthesis was required to obtain optimal polykaryon growth. Immunoelectron microscopy using a syngenic mouse MF2 cell antiserum and peroxydase labeling revealed a complete mixing and redistribution of the respective plasma membrane sites of MF2 and XC cells on polykaryon surface.

Animals↗
PubMed1975

A structural change of the plasma membrane induced by oncogenic viruses: quantitative studies with the freeze-fracture technique.

In BHK21 hamster cells a significant increase in density of intramembranous particles occurs in freeze-fractured plasma membranes after transformation by hamster sarcoma and polyoma viruses. A similar change has been observed in chick embryo cells infected and transformed by a mutant of Rous sarcoma virus thermosensitive for transformation, at both permissive and nonpermissive temperatures. There is also an increase in particle density in chick cells infected with the Rous-associated avian leukosis virus type 1. The newly appeared particles may represent the insertion of new proteins in hydrophobic regions of plasma membrane, in response to the action of oncogenic viruses.

Animals↗