Marianne Semmel

Études des complexes de colorants basiques avec le RNA

Abstract Complexes of basic dyes with RNA The binding of certain basic dyes (proflavine, pyronine, toluidine blue, acridine orange) by polyribonucleotides (ribosomal RNA, (A) n ·(U) n , (A) n ·(U) n ·(U) n , (I) n ·(C) n , which causes a red shift in the absorption spectra of the dyes, has been studied. The number of dye molecules bound per nucleotide and the association constants were determined as well as the influence of proflavine and acridine orange on the melting temperature of the polyribonucleotides. Evidence is presented showing that the first dye molecules are intercalated between the base pairs of the organized regions of polyribonucleotides. These dye molecules cause a partial disorganization of the macromolecule which permits subsequent binding of other dye molecules with smaller binding constant but the same spectral effect. Toluidine blue is specifically bound by (I) n ·(C) n , pyronine by (A) n ·(U) n . The secondary structure of the polyribonucleotides is generally stabilized by the dyes as shown by the difference between the absorption temperature of the dye and the melting temperature of the polyribonucleotide. When the secondary structure of the polyribonucleotides disappears at high temperatures, the dye is bound to the phosphates as evidenced by the blue shift of the absorption spectra of the dyes.

The interaction of basic dyes with ribonucleic acid

Abstract Ribonucleic acid reacts in vitro with basic dyes such as toluidine blue, acridine orange, and pyronine to provoke a shift in the absorption maximum of the dye, either toward a longer (negative metachromasy) or shorter wavelength (positive metachromasy). The direction of the metachromatic shift is dependent on both the relative concentration of the polymer to the dye and on the secondary structure and the chainlength of the polymer. In studies with synthetic polymers, RNA, and RNA-fractions, at known polymer-dye ratios, it was found that the length of the polymer chain determined the extent of positive metachromasy. On the other hand, negative metachromasy appears dependent on density of double-stranded regions in RNA molecules.

Isolation and characterization of surface membranes from chorioallantoic cells and chick fibroblasts.

Abstract Surface membranes were prepared from chorioallantoic cells and cultured chick fibroblasts by different methods. Mechanical disruption of cells followed by centrifugation through an aqueous two phase system and a sucrose gradient yielded a fraction composed mostly of surface membranes (enzymatic markers, cholesterol/protein ratio, phospholipid/protein ratio, electron microscopy). Results obtained by this method were fairly reproducible. Use of the method of Tremblay (sarkosyl-Mg crystals) yielded a mixture of cellular membranes, with great variations between experiments.

Host-range mutant of fowl plague virus (FPV): Comparison of the genome and virus proteins

Abstract A host-range mutant of fowl plague virus, which has the ability to grow in mammalian cells, has been investigated. It was found that one or two of the structural proteins were apparently smaller than the corresponding proteins of the wild-type virus which only multiplied in chicken cells. There was also a corresponding reduction in the size of one of the genome fragments.

Inhibition of Rous sarcoma virus-induced transformation by preinfection with rhabdoviruses.

In vivo preinfection of chicks with rabies virus (RV) or vesicular stomatitis virus (VSV) ts 1026 inhibits tumour formation after superinfection with Rous sarcoma virus (RSV). The degree of inhibition depends on the titre of the infecting viruses and the interval between rhabdovirus and RSV infection. In vitro, cells preinfected with VSV ts 1026 under non-permissive conditions and superinfected with RSV, are not transformed as judged by cell morphology, serum requirement for growth or the capacity to form colonies in soft agar, all these being the same as in uninfected cells. Doubly infected cells take up less deoxyglucose than cells infected with RSV only and more than cells infected with VSV only. RSV multiplication in inhibited in doubly infected cells: the supernatant fluid of these cells contains fewer focus-forming units and less reverse transcriptase activity than that of cells infected with RSV only. Doubly infected cells contain both VSV and RSV internal antigens 15 days after infection. The supernatant fluid of cells infected with VSV and maintained under non-permissive conditions inhibits transformation by RSV and multiplication of RSV, but not of VSV. Under non-permissive conditions, the rhabdoviruses undergo at least part of the infectious cycle, but no infectious virus is produced. RV antigen can be detected in the brain of parenterally infected chicks and VSV antigen in cells infected 15 days previously. We conclude that the inhibition of RSV multiplication and expression is probably due to one or more processes linked to the persistence of rhabdovirus components and that it cannot be attributed exclusively to interferon.

Differentiation of Burkitt lymphoma cells by hexamethylenbisacetamide

Hexamethylenbisacetamide (HMBA) can induce the Burkitt lymphoma Raji cells to enter the differentiation process as evidenced by the decrease of HLA-DR antigens. This event is preceded by a decrease of c-myc expression and of the phosphorylation of cellular proteins, due toeither a decrease of tyrosine protein kinase activity or an increase of tyrosine phosphatase activity. These three events form a sequence and are part of the genetic program for differentiation and growth though they may not be causally related.

Lipophilic proteins extracted from chick embryo cell cultures by different methods

Abstract Compounds containing both proteins and phospholipids were extracted by 3 different methods with organic solvents from labeled chick embryo cells cultured in vitro . The extracted material was analyzed by polyacrylamide gel electrophoresis (PAGE) and thin layer silica gel chromatography (TLC). The characteristics of these compounds are: 1. 1) Polypeptides of an apparent molecular weight comprised between 10 and 20 Kdaltons·are extracted by each of the 3 methods. Additional polypeptides of a molecular weight ranging from 20 to 70 Kdaltons are extracted with acid chloroform-methanol; with this method the highest yields are obtained. 2. 2) The phospholipid composition differs from that of the whole cell; it is enriched in phosphatidylserine and phosphatidylinositol. 3. 3) The compounds are soluble in organic solvents and in aqueous solvents containing SDS. 4. 4) Membrane enriched fractions contain more of these compounds than whole cells.

Interaction in vitro des acides nucléiques avec des alcaloïdes extraits de Vinca rosea et l'acide glutamique

Summary The vinca alcaloids and glutamic acid react with nucleic acids and cause a decrease of their Tm. Glutamic acid binds to DNA and poly (A) poly (U) and cosediments with these macromolecules in a sucrose gradient. The binding is probably due to weak electrostatic forces as the bonds are very sensitive to modifications of ionic strength.

Isolation of proteins with kinase activity and related to pp60 src from human cells.

A protein kinase activity (PK) was associated with immunoprecipitates between polypeptides of human lymphoblastoid cells of malignant origin (Raji cell line) or of their normal counterparts ( Priess cell line) and antibodies directed against avian pp60 src or against the carboxyterminal hexapeptide of pp60 src. Therefore, these human cells and Rous Sarcoma Virus (RSV) transformed avian cells share antigenic determinants of pp60 src and, in particular, its carboxyterminal sequence, as well as one of its functions, a protein kinase activity. The protein kinase from Raji cells phosphorylated predominantly tyrosine residues, that from Priess cells threonine residues.

The Effect of Ethidium Bromide on Lcells and Encephalomyocarditis Virus Replication

Summary Ethidium bromide inhibits multiplication of encephalomyocarditis virus and synthesis of infectious single-stranded virus RNA. Infectious double-stranded virus RNA and cellular RNA synthesis are inhibited to a lesser degree. It is suggested that the effect is due mainly to binding of the drug to double-stranded replicative virus RNA.