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Biomedical subjects

R Repanovici

Publications and source records attributed to R Repanovici.

At least 55 records · Page 3Linked to original sources
PubMedDate not supplied

Virus - tumor cell relationships. In vivo cocultivation of para-influenza type 1 (Sendai) virus and of Rous sarcoma virus (Schmidt-Ruppin strain) in mouse Ehrlich ascites carcinoma.

Co-infection of Ehrlich ascites carcinoma (EAC)-bearing mice with Sendai virus and Rous sarcoma virus (RSV) did not result in the formation of complete RSV. Sendai virus could be, however, propagated in this system over 8 serial passages. As demonstrated by immunofluorescence and complement fixation reactions, antigens specific to each virus were synthesized in EAC cells following either single or mixed virus infection. The virus progens also contained antigenic fractions incorporated from the host cell. The incomplete progens synthesized when RSV inoculation preceded that of Sendai virus possessed three polypeptide fractions characteristic of Sendai virus and one RSV-specific fraction.

Animals↗
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Effect of homologous tumor DNA on the evolution of SV40-induced hamster sarcoma.

DNA extracted from SV40-induced hamster sarcoma (SV40--HS DNA) increased the survival length of animals carrying the homologous tumor and--in some cases--inhibited the development of the tumor. The efficacy of the preparation was directly proportional to the number of administrations; it did not necessarily depend on the amount of SV40--HS DNA per dose. SV40 DNA had no favourable effect on the evolution of the SV40-induced tumor, which suggests that viral DNA does not represent the active component of the SV40--HS DNA preparations. Some possible mechanisms of the effect of homologous tumor preparations are discussed.

Animals↗
PubMedDate not supplied

Isolation of poly(A)-rich mRNA from the chorioallantoic membrane of Sendai virus-infected chick embryos.

Total RNA was extracted from the chorioallantoic membrane (CAM) of Sendai virus-infected chick embryos by the original Kecskeméthy-Schäfer method and by a modification of this technique, including phenol treatment, in order to ensure complete removal of proteins. The purity of the total RNA extracted by the modified technique was ascertained by spectral analysis. Chromatography on oligo(dT)-cellulose of the total RNA led to the isolation of poly(A)-rich mRNA--the material retained by oligo(dT)-cellulose and eluted with the buffer of the lowest ionic strength. The ability of the poly(A)-rich mRNA thus obtained to stimulate incorporation of 14C-leucine into protein was demonstrated in a cell-free protein-synthesizing assay system.

Allantois↗
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Preliminary data on the encapsulation of biologically active materials in liposomes.

Multilamellar and unilamellar phospholipid liposomes were prepared and investigated as regards their properties and the capacity of encapsulating biologically active materials, such as CrO4-(2-)ions, basic dyes, proteins, DNA, as well as Sendai virus particles. The efficiency of encapsulation ranged from 10% for CrO4-(2-)ions to about 80% for toluidine blue; it was found to depend not only on the type of encapsulated material, but also on the method used for liposome preparation and on liposome composition.

Animals↗
PubMedDate not supplied

[Molecular mechanism of the replication of several DNA viruses].

Study of the replicative mechanism of viruses is extremely important, since the knowledge of the events taking place at a molecular level can contribute to new antiviral product elaboration. A unique pattern of the DNA virus replication cannot be given, because every virus family has its own mechanism of replication. Investigations were conducted on the replication of two groups of viruses of major importance in human pathology: the hepadnaviruses and the herpesviruses, which are involved not only in acute infections, but also in some cellular transformations and even in cancerogenesis. It was shown that the replication mechanism of the hepadnaviruses has several points in common with retroviruses, fact which places them in a rather peculiar position among the DNA viruses. On the other hand, the herpes viruses have their own characteristics such as the four genome isomeres, whose significance is yet unclear. The viral message transcription and translation stages, as well as the mechanism of replication of the genome are described.

DNA Replication↗
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Research in the field of nucleic acids performed in the "Stefan S. Nicolau" Institute of Virology.

A review is made of the research in the field of nucleic acids performed in the "Stefan S. Nicolau" Institute of Virology. The results obtained as regards the infectivity of viral nucleic acids, the oncogenic capacity of nucleic acids extracted from tumors, the isolation, characterization, physicochemical and biological activity of viral and cellular nucleic acids, as well as some achievements in recombinant DNA technology, are briefly presented.

Academies and Institutes↗
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Stimulation by inlfuenza virus RNA of 3H-phenylalanine incorporation in a cell-free system.

Purified and unpurified cell-free systems prepared from the chorioallantoic membrane of embryonated eggs were tested for polypeptide synthesis in the presence and absence of influenza virus RNA. Both systems exhibited an endogenous messenger activity determining 3H-phenylalanine incorporation into polypeptides in the absence of virus RNA. However, addition of influenza virus RNA to the systems clearly stimulated amino acid incorporation into polypeptides, offering the possibility of studying some aspects of the viral protein biosynthesis mechanism.

Amino Acids↗
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Investigations in the field of recombinant DNA technology performed in the "Stefan S. Nicolau" Institute of Virology.

A brief review is provided of the investigations in the field of recombinant DNA technology started in 1979 in the Central Laboratory for Nucleic Acids within the "Stefan S. Nicolau" Institute of Virology. The research efforts have been focused on the following main objectives: optimization of vector extraction, isolation and purification of restriction enzymes and of DNA ligase T4, transformation and transfection experiments, construction of recombinant DNA.

Academies and Institutes↗
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Investigation of the effect of cellular and viral nucleic acids on certain virus infections. Note 2. Effect of nucleic acids on virus multiplication in cell cultures.

Treatment of cell cultures with different natural nucleic acids prior to inoculation of herpes simplex virus type 1 led in certain cases to an obvious reduction in infectant titer. The reduction was maximum at a dose of 50 micrograms nucleic acid/culture tube and it was not dependent on the nature of the nucleic acid preparation. The antiviral effect of nucleic acids was enhanced by complexation with intercalation agents such as ethidium bromide or violamycin BI. No detectable amounts of interferon could be made evident in cell cultures treated with chromosomal DNA under conditions leading to a reduction by 1.75 log in infectant titer.

Aminoglycosides↗
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Polypeptide changes in Sendai virus-infected cells.

The appearance of virus-specific proteins in Sendai virus-infected chick embryo fibroblasts and chorioallantoic membrane cells was studied by high resolution SDS-polyacrylamide gel electrophoresis. All the structural Sendai virus polypeptides, as well as the nonstructural virus polypeptide termed B could be identified in the total lysates of infected cells. Only the structural virus polypeptides NP, P and M were found in the ribosome fraction of virus-infected cells; these additional polypeptides were removed from the ribosome surface by washing the 1 M NH4Cl.

Animals↗
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The effect of violamycin BI on different biological systems. Note I. The action of violamycin BI on cell cultures infected or not with herpes simplex virus type 1.

The effect of violamycin BI (VBI) was investigated in different cell substrates, infected or not with herpes simplex virus type 1 (HSV-1), strains VR3 and Rapp-1. The cytotoxic dose of VBI was established in calf kidney and human embryo cell cultures. Low drug concentrations induced moderate cytotoxic changes, allowing the study of the cells for 4-6 days. The action of VBI on HSV-1 was evident mostly in the early phases of the virus multiplication cycle. The antiviral effect of VBI was due both to the direct action of the drug on HSV and to its interaction with the nucleic acids of the host cells supporting HSV multiplication in their nuclei.

Aminoglycosides↗
PubMedDate not supplied

EPR and Mössbauer spectroscopy investigations on the metal ion contents of Sendai virus components.

EPR and Mössbauer spectroscopy indicate that Sendai virus contains iron ions in paramagnetic states. Spectral data show that the iron ions are in an oxidized form (Fe3+), having low and high spin states (S = 1/2 and S = 5/2). On enrichment of Sendai virus with 57Fe, the concentration of Fe3+ ions substantially increases in the virus preparations. The Fe3+ ions in the high spin state appear to be tightly bound to the virus components; they are not significantly removed by dialysis. The five main proteins separated by SDS gel electrophoresis from 57Fe-enriched Sendai virus contain the signal corresponding to the presence of Fe3+ ions in the high spin state. The concentration of Fe3+ ions is, however, about five times higher in the HN polypeptide than in the other four components. It is suggested that Fe3+ (5/2) ions might be a structural component of the Sendai virus HN polypeptide.

Electron Spin Resonance Spectroscopy↗
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Effect of biologically active compounds (anthracyclines and ethidium bromide) on some membrane-mediated processes in the course of viral infection. Investigations on a prokaryotic (bacteriophage-bacterium) system.

Anthracycline antibiotics--violamycin B1 and adriamycin--have an obvious effect on the efficiency of phage lambda L47.1 DNA transfection into E. coli Q358 cells. Treatment with anthracyclines of either phage DNA or bacterial cells results in a marked decrease in the number of transfectants per microgram DNA. On the other hand, adsorption of phage lambda gt WES to E. coli LE392 is considerably modified by exposure to anthracyclines of either the phage or the host cells.

Adsorption↗
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Study of several genetic markers of two recombinants derived from autochthonous influenza virus type A strains.

Two recombinants derived from autochthonous influenza virus type A strains were studied as regards neuraminidase activity, the rate of elution from chicken RBC and the sensitivity to nonspecific horse serum inhibitors. Neuraminidase activity was lower in the A(H1N1) recombinant and in its collection and wild-type parents belonging to the same subtype than in the A(H3N2) recombinant and parental strains; the elution rate was much higher in the former than in the latter. In contrast to the parental strains, both recombinants were resistant to horse serum inhibitors.

Antiviral Agents↗