Estimation of avidin activity by two methods.

The biological activity of avidin was estimated by two different methods. The spectrophotometric method used the avidin titration with biotin in the presence of 4 hydroxiazobenzen-2'carboxilic acid as indicator. In the radioisotopic determination the titration with tritiated biotin was accomplished. Both methods led to the same results, but the spectrophotometric one is less avidin expensive and more rapid, being more convenient.

The control of some viral epidemics by antiepidemic programmes elaborated by an expert system.

A base of data for viral epidemiological studies is presented containing correlation between outer symptoms (observable characteristics of the mass morbid phenomena), inner symptoms (characteristics of intensity of elementary processes implied in the virosis propagation) and influencing factors (risk or protective ones). A resolutive nucleus of processing these is divided in to three parts: an inductive one (specification of the mentioned correlations, of the mathematical model and its equation solutions); a deductive one (explaining or prognosing the epidemiological evolution); a decisional one (specifying the antiepidemic services, necessary for a possible or desired reduction of the morbidity).

[35 years of research and study in radiovirology at the Stefan S. Nicolau Institute of Virology]. / Trente-cinq ans de recherches et d'études dans le domaine de la radiovirologie à l'Institut de Virologie "Stefan S. Nicolau".

The report presents researches conducted in the field of radiovirology, these 35 last years, at the Radiovirology Central Laboratory of the Academy of Medical Sciences: ionizing radiation little dose effects on the evolution of virus infections, virus migration through the infected organism and its stocks in different organs, intracellular synthesis of viruses, radioisotope characterization of viral nucleic acids, studies of viral molecular biology, radioimmunologic diagnosis of virus diseases, virus inactivation and sterilization through ionizing radiation, space virology studies within "Intercosmos" research program.

[The potentials for immunization against influenza using liposome-incorporated viral surface antigens]. / Possibilités d'immunisation contre la grippe à l'aide d'antigènes viraux de surface incorporés aux liposomes.

Studies were conducted using uni- and multilamellar liposomes to establish optimum conditions for influenza antigen incorporation in view of their transport to the target cells for experimental influenza prophylaxis in hybrid white mice. Radiometric determinations showed a good level of preparation purification, a good efficiency of incorporation in liposomes of the active biological material, the liposome linked radioactivity distribution among different organs. Charged liposomes induced solid and long lasting resistance against influenza control infection.

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.

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.

Investigation of the effect of cellular and viral nucleic acids against experimental influenza virus A/PR8/34 (H1N1) infection in mice.

Treatment of mice with different cellular nucleic acids prior to inoculation of influenza virus A/PR8/34 (H1N1) conferred--in some cases--a nonspecific protection against the experimental infection. The optimal amount of nucleic acid was 400 micrograms/mouse, irrespective of the origin or type of the macromolecule.

Investigations concerning the action of serveral chemical and biological agents on HBsAg.

Native and purified HBsAg preparations were subjected in vitro to the action of cetylpyridinium bromide (Bromocet), hibitan-chlorhexidine (Hibiscrub), chloramine B and propolis extract, at different concentrations and for various time intervals. The effect of these agents on the serological reactivity of HBsAg was tested by electroimmunodiffusion (EID) and radioimmunoassay (RIA). Chloramine B and the propolis extract had a significant inhibitory effect-ascertained by both EID and RIA - on purified HBsAg, but not on the native preparation. The inhibition exerted by Bromocet and Hibiscrub indicated by EID results was not confirmed by RIA.

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.

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.

Investigations of the antiviral activity of some nitroso-urea derivatives. Inhibitory action of the IOB-252 nitroso-urea derivative on vaccinia virus incell cultures.

The nitroso-urea derivative IOB-252 was administrered in monkey kidney cell cultures in a concentration of 40 mug/ml 24 hours before inoculation of vaccinia virus and maintained afterwards in a concentration of 25 mug/ml. The drug inhibited vaccinia virus multiplication, hemagglutinin synthesis and late cytopathic effect, but did not prevent early cytopathic lesions. IOB-252 inhibited the synthesis of interferon initiated by a viral inductor and blocked the antiviral effect of an exogeneous interferon. The mechanism of action of the drug is discussed.

Isolation, purification and characterization of polypeptides of influenza and parainfluenza viruses. Note III. Polypeptides of three influenza virus strains isolated in Romania.

An analysis is presented of the nature, number and relative molecular mass of the polypeptides of three influenza virus strains-A/Romania 1/73 (H3N2), A/Romania 1/75 (H3N2), and B/Romania 34/74-isolated during different epidemic outbreaks. The results obtained indicate some similarities between the protein subunits of the two influenza A virus strains (as concerns virus surface and nucleocapsid components) and point out the particular properties of the influenza B strain.