[Morphological characteristics of the brain lesions in mice infected with a homogenate of L cells latently infected with the scrapie agent]. / Morfologicheskie osobennosti porazhenii mozga myshei, zarazhennykh gomogenatom kletok L, latentno infitsirovannykh agentom skrepi.

Degeneration of neurons of the Ammon horn lower branch both in the early and terminal stages of the disease of mice infected with the homogenate of L cells latently infected with the scrapie agent (the L-S system) was frequently detected alongside with brain lesions typical of slow infections (vacuolation). Examinations of chromosomes in metaphase plates of L-S cells carried out by several methods including the TAC system for texture analysis of the image (Leutz, BRD) revealed three marker chromosomes new for continuous L cells, the appearance of true chromatid translocations as well as significant changes in chromosome numbers. Besides, ultrastructural features of L-S cells at later stages of cultivation were revealed. It is assumed that the active effect of the scrapie agent on L cells infected with it resulted in the emergency of a new antigen capable to induce selective affection of the neurons of the Ammon horn lower branch in susceptible mice.

[Standardization of the conditions for measuring the specific fluorescence intensity in continuous cell cultures infected with variants of the Japanese encephalitis virus]. / Standartizatsiia uslovii izmereniia intensivnosti spetsificheskoi fliuorestsentsii v zarazhennykh variantami virusa iaponskogo éntsefalita kul'turakh perevivaemykh kletok.

The use of modernized photometric accessories to a model microscope manufactured by the Leningrad Optico-Mechanical Amalgamation (USSR), as well as the practical application of innovations facilitating and standardizing research work, has made it possible to obtain objective data indicating the presence of significant, direct, linear correlation between infectious activity and the intensity of fluorescence emitted by fluorescent antibodies bound with the antigen of 11 studied variants of Japanese encephalitis virus in continuous cell lines. The study of the dynamics of fluorescence intensity permitted the objective evaluation of the previously revealed regularity in the increase of the intensity of the induced fluorescence of Japanese encephalitis antigen in continuous cell cultures.

[Karyological characteristics of continuous mouse cell lines infected with the scrapie agent]. / Kariologicheskaia kharakteristika perevivaemykh linii myshinykh kletok, infitsirovannykh agentom skrepi.

A karyological study of murine cell line L, latently infected with different strains of the scrapie agent (Compton and C-506) showed that the both variants number of chromosomes and the number of Robertson's translocations of chromosomes decrease insignificantly with an increase in the time of subcultivation. The use of the C-method of differential chromosome staining revealed four new analogous chromosomes in both experimental cell lines. This phenomenon is probably specific for this infected cell model.

[Infectious activity of cell fractions isolated from the brain of mice with scrapie]. / Infektsionnaia aktivnost' fraktsii kletok, vydelennykh iz mozga myshei, bol'nykh skrepi.

The agent of scrapie was found to induce clinically similar diseases in BALB/c and NIH mice but differing in the duration of the incubation period (155-180 days and 110-140 days, respectively) and pathomorphological manifestations. Differentiated examinations of a brain cell pool from mice with scrapie revealed more infectious activity not neutralized with nucleases and pronasa in membrane-free cell fractions than in fractions of slowly sedimenting membranes.

[Latent infection of continuous L23 cells caused by the agent of scrapie]. / Latentnaia infektsiia perevivaemykh kletok L23, vyzvannaia agentom skrepi.

Two models of latent infection of continuous L23 cells caused by scrapie agent were developed using the method of cell cloning as well as DEAE-dextran and lidase preparations. The infectious activity was found only in cell homogenate L-C and L-506 (cells of clone L23 latently infected with the Compton and C-506 strains of the scrapie agent). A direct relationship between the infectious activity of the cell homogenate and the intensity of brain lesions revealed by morphological examinations of brain sections from infected mice was observed. The cytoplasm of L-C and L-506 cells became strongly vacuolated, piknosis of the nuclei and delay in the cell growth rate were noted. Cytogenetic studies established changes in the model class of the experimental cultures as well as the appearance of rearranged chromosomes.

[Persistence of Japanese encephalitis virus clones in continuous HeLa cells]. / Persistentsiia klonov virusa iaponskogo éntsefalita v perevivaemykh kletkakh HeLa.

Some virological and biological properties of the H-N and H-P systems (cells of HeLa line clone persistently infected with the Nakayama and Peking I strains of Japanese encephalitis virus, JE, respectively) were studied. A feature distinguishing these systems from all previously described models of persistent infection (PI) of vertebrate cells with JE virus consisted in the lack of visible signs of virus-specific degeneration of the cultures. Attempts to free PI cells from persisting viruses by changing cultivation conditions or with virus-specific antibodies failed. The "zone" phenomenon frequently observed in PI as well as resistance of the cultures to superinfection with isologous viruses only appeared to indicate the presence of interfering particles in the H-N and H-P systems.

[Modeling of persistent HeLa cell infections caused by different Japanese encephalitis virus clones]. / Modelirovanie persistentnykh infektsii kletok HeLa, vyzvannykh raznymi klonami virusa iaponskogo éntsefalita.

The authors developed two models of persistent infections of a HeLa cell clone with mildly pathogenic clones of the Nakayama and Peking I strains of Japanese encephalitis virus. The distinguishing features of these models included the noncytocidal nature of the infectious process, predominance of the small-plaque phenotype, further decrease of the infectious properties of the persisting viruses. Altogether during the observation period 84 subpassages of each of the two systems were made without any visible signs of cell degeneration.

[Natural foci of viruses borne by Phlebotomus papatasi in the USSR according to a serologic study of the population]. / Prirodnye ochagi virusov, perenosimykh Phlebotomus papatasi, v SSSR po dannym serologicheskogo obsledovaniia naseleniia.

Seven hundred sixteen blood serum specimens from residents of presumable foci of phlebotomus fevers in Turkmenia, Tajikistan, Uzbekistan, Azerbaijan, and Moldavia were examined by the neutralization, complement fixation, hemagglutionation-inhibition and indirect immunofluorescence tests for the presence of antibody to viruses of the group of phlebotomus fevers (Sicilyan, Neapolitan, and Karimabad) and to rhabdovirus isfahan transmitted by phlebotomus papatasi. For the first time, antibody to Karimabad and Isfahan viruses were found in residents of the Central Asian republics. Antibody to Sicilyan and Neapolitan fevers were found in residents of all the republics examined. Data have been obtained indicating probable pathogenicity of Isfahan virus for man.

[Persistence of lymphocytic choriomeningitis virus in a transplantable line of Detroit-6 cells]. / Persistensiia virusa limfotsitarnogo khoriomeningita v perevivaemoi linii kletok Detroit-6.

Defective LCM virus was found to persist in Detroit-6 cells. The persisting virus was not infectious for susceptible mice and some cell cultures. Its antigenic properties were enhanced to detectable levels in the CFT by cocultivation with LSV5 cells only. No reversion to its pathogenic properties, however, occurred either after 8 subpassages of the cocultivated cells or after blind passages of these cells in suckling mouse brains. The cytogenetic analysis, and the pattern of antigen fluorescence (IIF) revealed similarities between HeLa and D-6 cell lines persistently infected with LCM virus. The highest intensity of LCM virus antigen coincided with the period of maximum miotic activity of D-6-LCM cells, indicating a correlation between synthesis processes in the cells and reproduction of the persisting virus. Upon superinfection of D-6-LCM cells with homo- and isologous viruses no increase in the percentage of the antigen-containing cells was observed. No detectable interferon was found in the D-6-6CM system.

[Persistent infection of pig embryo kidney cell cultures caused by a variant of tick-borne encephalitis virus]. / Persistentnaia infektsiia kul'tur kletok pockek émbriona svin'i, vyzvannaia variantom virusa kleshchevogo entsefalita.

The results of modelling and study of persistent infection of pig embryo kidney cell cultures (PEK) with MF variant of tick-borne encephalitis (TBE) virus are presented. In the life of chronically infected cultures periods of formation and stabilization were observed which were characterized by different types of relationships between the persisting virus and the cells. By the characters under study the persisting virus did not differ significantly from the initial MF variant. Inoculation of PEK and BHK-21 cell monolayers with samples of DNA from chronically infected cultures permitted to isolate transfected agents. Their identification by the neutralization tests and the indirect immunofluorescence procedure confirmed that they belonged to TBE virus. It is suggested that the mechanism of TBE virus persistence in PEK-MF system is based on the integration of TBE virus genome with DNA of chronically infected PEK cells.

[Comparative study of 2 transplantable lines of murine L cells]. / Sravnitel'noe issledovanie dvukh perevivaemykh linii myshinykh kletok L.

A continuous line of mouse L cells chronically infected with SV5 paramyxovirus differs from mouse L0 cells free from this virus in the mitotic activity and karyologic features. The LSV5 line is characterized by inhibition of the mitotic activity, a decrease in the number of chromosomes and the presence of the marker chromosome. LSV5 and L0 cell cultures do not differ in the number of pathological mitoses, structural aberrations of chromosomes and the cytomorphological picture. The persisting SV5 virus can be detected in LSV5 line cultures by a number of methods (immunofluorescence, virological methods, etc.).