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S Rousset

Publications and source records attributed to S Rousset.

At least 37 records · Page 2Linked to original sources
PubMed1990

Molecular analysis by electron microscopy of the removal of psoralen-photoinduced DNA cross-links in normal and Fanconi's anemia fibroblasts.

The induction and fate of psoralen-photoinduced DNA interstrand cross-links in the genome of Fanconi's anemia (FA) fibroblasts of complementation groups A and B, and of normal human fibroblasts, were investigated by quantitative analysis of totally denatured DNA fragments visualized by electron microscopy. 8-Methoxypsoralen (5 x 10(-5) M) interstrand cross-links were induced as a function of the near ultraviolet light dose. With time of postexposure incubation, a fraction of interstrand cross-links disappeared in all cell lines. However, 24 h after treatment, this removal was significantly lower in the two FA group A cell lines examined (34-39%) than in the FA group B and normal cell lines (43-53 and 47-57%, respectively). These data indicate that FA cells are at least able to recognize and incise interstrand cross-links, as normal cells do, although group A cells seem somewhat hampered in this process. This is in accord with data obtained on the same cell lines using another biochemical assay (D. Papadopoulo, D. Averbeck, and E. Moustacchi. Mutat. Res., DNA Repair Rep., 184: 271-280, 1987). Since the fate of cross-links in FA constituted a controversial matter, it is important to stress that two different methodologies applied to genetically well defined cell lines led to the same conclusions.

Anemia, Aplastic↗
PubMed1987

Homologous recombination intermediates between two duplex DNA catalysed by human cell extracts.

Using as substrates, 1: the replicative form (RF) of phage M13 mp8 in which the reading frame of the lac Z' gene was disrupted by insertion of an octonucleotide, and 2: a restriction fragment one kb long, containing the functional lac Z' gene (isolated from wild type M13 mp8), we show that nuclear extracts from human cells (3 lines tested) promote the targeted replacement of the altered sequence by the functional one. Following incubation with the extracts, the DNA's were introduced in JM 109 bacteria (rec A- and lac Z'-) which were grown in presence of a colorimetric indicator of beta-galactosidase activity. Homologous recombination gives rise to the genotypical modification: lac Z'+ instead of lac Z'- in the bacteriophage DNA. This is revealed by phenotypical expression of the lac Z' gene product in replicating bacteriophage, i.e. the formation of blue instead of white plaques. The frequency of recombination (blue/total plaques) is increased by a factor of 50-80 as a function of protein concentration and of incubation time. The maximal frequency observed is 5 X 10(-5). There is no increase over the background when extracts are boiled. Electrophoresis and electron microscopy of DNA's incubated with the extracts show the formation of recombination intermediates with single strand exchange. Restriction analysis of recombined DNA confirms that the process corresponds to targeted sequence exchange. These data allow to propose three steps for homologous recombination between two duplex DNA's: i) unpairing of the two duplexes; ii) single-strand exchange and synaptic pairing; iii) resolution of the cross-junctions. The three steps correspond to those predicted by the gene conversion model of Holliday.

Cell Line↗
PubMed1987

Cell distribution and antigenic properties of mammalian sarcolectins.

Sarcolectins are present in a great variety of tissues from mammalian origin. Such substances were observed to be secreted from cultures of human embryonic fibroblasts, human osteosarcoma and rat Rous sarcoma transformed cells and could be extracted from TG 180 Crocker Sarcoma or normal human placenta. All sarcolectins tested here, were comparable by their physicochemical properties to those previously reported in hamster or human sarcomas. Indeed, they are proteins or glycoproteins, resistant to pepsin and migrate in SDS-PAGE in the 65 kDa area. They agglutinate cells with an affinity for simple sugars and degrade previously established interferon-induced antiviral resistance. Considering the hamster sarcolectin as reference in this comparative study, both differences and similarities in the antigenic properties of mouse, rat and human sarcolectin variants were demonstrated. An indirect immunofluorescence assay showed that sarcolectins were specifically labelled on the cell surface but not detected in the cytoplasm after methanol or acetone permeabilization of the membrane. By electron microscopy, using immunoperoxidase labelling, sarcolectins can be localized on the surface of normal, transformed, human or rat cells. Only limited segments of normal cell membranes were labelled, while transformed cells were frequently stained on their whole surface. Other known extracellular proteins, such as fibronectin and collagen, did not share common antigenic determinants with sarcolectins.

Animals↗
PubMed1985

Factors involved in interferon-induced or cholera toxin-induced steroidogenesis in Y-1 mouse adrenal tumour cells.

In addition to its antiviral effect, interferon, at high concentrations, stimulates steroidogenesis and provokes cell rounding in Y-1 mouse adrenal tumour cells. This stimulation was inhibited by cytochalasin B and colchicine. In contrast, dibutyryl cAMP and cholera toxin, also able to induce steroid production and cell rounding, increased steroid production even in the presence of these cytoskeleton-disrupting agents. The initial trigger for interferon or cholera toxin thus probably involves a distinct receptor organization. However, since both inducers increased cAMP synthesis in this differentiated cell line, the further metabolic steps of ketosteroid production could be the same.

Adrenal Gland Neoplasms↗
PubMed1984

Chromatin structure and nucleic acid synthesis in human lymphocyte activation by phytohemagglutinin.

Alterations in chromatin structure were explored as a function of time following phytohemagglutinin (PHA) activation of human lymphocytes. Nuclear refringency (related to chromatin status), ultrastructural changes, and modifications of nucleic acid synthesis were compared. Chromatin dispersion was observed within 20 min of stimulation, with a concomitant increase in [3H]uridine incorporation; both were inhibited by actinomycin D. Recondensation of chromatin had occurred at 60 min when RNA synthesis was still increasing. The early chromatin dispersion thus was a reversible step and one of the most striking cellular events during the first phase of PHA activation. Late chromatin dispersion of blastic cells during the second phase of PHA response (after 24 h) was related to DNA synthesis in mitotic cells. This step was also inhibited by actinomycin D. These results suggest a relationship between the morphological changes in chromatin structure and the induction of RNA and DNA syntheses. The regulation of transcriptional and replicational states of the nucleus is discussed in terms of modifications of chromatin structure, considering PHA-induced calcium and cyclic nucleotide metabolism and interleukin II receptor expression.

Adult↗
PubMed1984

Intestinal lesions containing coronavirus-like particles in neonatal necrotizing enterocolitis: an ultrastructural analysis.

Since the outbreaks of neonatal necrotizing enterocolitis occurring in maternity hospitals of Paris and suburbs in 1979-1980, it has been possible to examine by light and electron microscopy gut specimens from ten newborns with this illness. Coronavirus-like particles, enclosed in intracytoplasmic vesicles of damaged epithelial cells of the intestinal mucosa, were observed in the small intestine, appendix, and colon. The ultrastructural study, supported by bacteriologic findings, suggests the role of coronavirus-like particles in the appearance of the lesions. Secondary proliferation of mainly anaerobic bacteria, probably responsible for pneumatosis, may aggravate the disease.

Appendix↗
PubMed1982

Association of coronavirus infection with neonatal necrotizing enterocolitis.

From the clustered occurrence of numerous cases of necrotizing enterocolitis in newborns, it was possible to associate this disease significantly with infection due to coronavirus-like agents. Prematurity or low birth weight did not seem to affect the development of the disease, at least during the present epidemic. However, associated gas-producing bacteria could influence its severity and play a role in the appearance of pneumatosis. In many aspects the human disease is reminiscent of experimental necrotizing enterocolitis obtained by infection of germ-free newborn animals, as reported in the literature.

Antibodies, Viral↗
PubMed1981

Reorganization of the cytoskeleton by interferon in MSV-transformed cells.

beta and gamma interferons were found to enhance the organization of microfilaments, intermediate filaments, and fibronectin in the murine sarcoma virus (MSV)-transformed cell line. Furthermore, both interferons increased the number of intermediate-type junctions. Sodium butyrate was also found to act in a similar way and, when associated with interferon, an additive effect was observed. In the cell line, cultured for many passages in the presence of beta interferon (MSV-IF+), the cytoskeletal network and the extra-cellular matrix were highly developed and were reminiscent of a normal cell. These results could explain some of the biological actions of interferon, such as increased cell adhesion to the substratum and decreased cell motility.

Actins↗
PubMed1981

Interferon effect on collagen and fibronectin distribution in the extracellular matrix of murine sarcoma virus-transformed cells.

The transformation of murine BALB/c embryonic fibroblasts by murine sarcoma virus, Moloney strain, followed by prolonged treatment with murine interferon, resulted in the appearance of a new cell population (MSV-IF+). These MSV-IF+ cells are characterized by the recovery of a normal phenotype, contact inhibition, and lack of colony formation in agar. This phenotypic change of the MSV-IF+ cells is associated to the neosynthesis of a dense fibrous matrix beyond the cell periphery. Ultrastructural studies using peroxidase-labeled antibodies enabled us to localize the extracellular distribution of fibronectin and collagen in the MSV-IF+ cell line, compared to normal BALB/c and murine sarcoma virus-transformed cells. In parallel, a significant increase of collagen and fibronectin deposit in the intercellular space of interferon-treated murine sarcoma virus-transformed cells was observed.

Animals↗
PubMed1980

[Association of coronavirus infection with hemorrhagic entercolitis in newborn infants].

The existence of a widely spread corona virus epidemic enabled us to associate this infection with necrotizing hemorrhagic enterocolitis in newborn infants. Virus is detected in the stools by direct electron microscopic examination. Virions are found agglutinated in the gut during convalescence, as they are by circulating antibodies. Arguments supporting a possible etiological role of this infection are given.

Antibodies, Viral↗
PubMed1980

Excretion of hepatitis B surface antigen particles from mouse cells transformed with cloned viral DNA.

A plasmid containing two cloned hepatitis B virus genomes in a tandem head-to-tail arrangement has been introduced into mouse fibroblasts by using cotransformation with the cloned herpes simplex virus thymidine kinase gene. Several copies of the plasmid were integrated into high molecular weight cellular DNA. The original tandem structure of the hepatitis B virus DNA was conserved. Hepatitis B surface antigen was synthesized by all the 15 clones examined. The other viral antigens were not detected. The surface antigen was excreted into the cell culture medium as particles having the same characteristics as those found in human serum. It is estimated that 2-4 X 10(4) particles were produced per mouse cell per 24 hr in two clones. This value corresponds to approximately 2-4 X 10(6) surface antigen polypeptides per cell per 24 hr.

Animals↗
PubMed1978

[Application of immunoelectron microscopy to the detection of viruses in a water medium].

Adenoviruses were immersed in demineralyzed and deionized water for 5 days. The water was subsequently analyzed by Immuno-Electron-Microscopy for detection of viral particles. An attempt of quantation was also made on control, untreated particles. Viruses dispersed in water can be detected by the technique employed but quantitation is limited by the heterogeneous dispersion of the particles on the grids.

Adenoviridae↗