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Biomedical subjects

L M Popa

Publications and source records attributed to L M Popa.

50 records · Page 3Linked to original sources
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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↗
PubMedDate not supplied

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↗
PubMedDate not supplied

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↗
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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 recombinants derived from autochthonous influenza virus type A strains.

Simultaneous inoculation of chick embryos with a standard laboratory influenza virus--A/PR8/34 (H0N1)--and with an autochthonous epidemic strain--belonging to the antigenic subtype A(H1N1) of A(H3N2), respectively--resulted in the isolation of two genetic recombinants, designated R1IVN (H1N1) and R2IVN (H3N2). Each recombinant was antigenically identical to its wild-type parent and exhibited a hemagglutinating titer in chick embryos about 4-fold greater than that of the autochthonous parental strain.

Animals↗
PubMedDate not supplied

Specific targeting of human papillomavirus type 16 E7 oncogene with triple-helix forming purine oligodeoxyribonucleotides.

Molecular mechanical calculations (computer modelling), optical DNA melting experiments and co-migration assay were used to assess stable helix formation at homopurine--homopyrimidine-rich target sites present in the human papillomavirus type 16 E7 oncogene (positions 656-673 on the genome map). The target sequence, either present in the E7 oncogene obtained by PCR technique or prepared from oligodeoxyribonucleotides (ODNs), can be specifically recognised by different 17-merpurine ODNs designed to form antiparallel or parallel triple helices. These in vitro experiments realised with rather long purine ODNs having a high degree of specificity open the way for in vivo tests focused on E7 oncogene targeting and suppression.

Base Sequence↗