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Twenty-six cultures were prepared by the cultivation method. Continuous cells lines (IK-10 and IK-12) were obtained in two cases, in the rest short-lived cell cultures were prepared. All the isolated cell cultures were studied by transmission electron microscopy. Abnormal lymphoblasts were detected in some cell cultures isolated from the blood and lymph nodes of mycosis fungoides (IJ-137, IK-140, IK-142, IK-143) and Kaposi's sarcoma patients (IK-145). Cell population consisted of small, medium, and large lymphocytes. Electron microscopic examination has revealed retroviruses in IK-143 culture, isolated from the lymph node of a patient with mycosis fungoides. Morphologically these particles were typical of type C oncoviruses, 120-140 nm in diameter, with a spherical core in the center of the virion.

Extracellular population of oncovirus of continuous human myeloma RPM18226 cells contains type D virions in addition to morphological types of A and C particles. Nucleoids of type D oncoviruses are encapsulated. Peculiar contacts morphologically similar to slit-like links between eucaryots were found between adjacent extracellular RPM18226V virions. Viral type A cores are formed both in any part of the cell hyaloplasm and on its surface. Comparative study of the ultrastructure of RPM18226V and some other retroviruses showed RPM18226V to be structurally and morphogenetically identical with squirrel monkey virus and, accordingly, should be classified in the group of type D oncoviruses (Retroviridae family, Oncoviridae subfamily, genus Oncovirus D).

The ultrastructure of hybridoma cells cultured with 5.10(-4) centrophenoxine (CP) has been studied. It is shown that CP effects hybridomas and prevents retrovirus exocytosis. The effect of CP on Ca-calmodulin system associated with cytoskeleton is suggested.

Splenomegaly characterised by myeloid metaplasia was induced in BALB/c mice by the injection of antigens and immunostimulants. In difference from leukemoid reaction, this syndrome was transmissible both by the plasma and by the splenic cells. Small virus-like particles (30--50 nm) were revealed in the plasma, and RNA-containing viruses of type C--in the splenic cells.

The properties of murine oncornavirus produced by cells of spontaneous lymphosarcroma of CC57Br mice are described. In addition to the properties common for C-type RNA tumor viruses such as 60-70 S high molecular weight RNA, the presence of RNA-directed DNA polymerase and murine gs I (intraspecies) antigen and typical morphology in electron microscope, etc., the virus under study is characterized by instability of virions, unusual features of the DNA polymerase system and by the absence of demonstrable oncogenicity either in laboratory animals or in tissue cultures.

Electron microscopic examinations of KLChKM (human embryo cells spontaneously contaminated with mouse cells) cell cultures revealed extracellular oncornaviruses of A and C types and intracisternal virions of A type which in their submicroscopical organization and morphogenesis were identical to oncornaviruses of mouse L cells. Also "minimal forms" (MiF) of oncornaviruses of A and C types the diameter of which was 30--70 nm were found. MiF of oncornaviruses were found to be formed in the process of budding through the cytoplasmic membrane or membranes of intracellular vacuoles.

The effect of BCG infection of L929 cells on replication of oncovirus type C was studied. Ultrathin sections of the BCG-infected culture were examined electron microscopically 1, 3, 6, 8, and 10 days postinfection. Most microorganisms with the morphology typical of mycobacteria were found inside phagosomes. The number of extracellular virions as well as budding and abnormal forms per one cell contour was counted. BCG-infected cells were found to produce significantly more virus than the controls. The difference was maximal 3 days postinoculation. Possible reasons for the increased oncovirus production by continuous cell lines after infection with BCG are discussed.

FLK cell culture chronically producing bovine leukemia virus (BLV) and spontaneously contaminated with mycoplasma (M. sp.) was studied by electron microscopy. Information on the features of the ultrastructural organization of M. sp. and its direct relationships with BLV was obtained. BLV virions are capable of adsorbing on mycoplasma surface and penetrate inside, apparently in the course of phagocytosis. In the cytosole of M. sp. free-lying BLV virions devoid of the limiting membrane were found. In FLK cells both agents were regularly produced in high amounts causing no signs of death of the cell culture itself. From the foregoing, the FLK cells--BLV-M. sp. system appears to be quite balanced.

The method of differential centrifugation was used for concentration and purification of the minimal form of oncornaviruses type A and C. The structures showed heterogeneous distribution in sucrose density gradient and formed a peak in the zone of 1.135 g/ml. Electron microscope examinations of negatively stained preparations showed that the size of the minimal forms of oncornaviruses type A and C was 25-60 nm, the diameter of nucleoids 10-30 nm.

Three peaks of 14C-radioactivity with buoyant densities of 1.23--1.24, 1.26 and 1.29 g/ml were detected in a cytoplasmic extract of J-96 cells upon equilibrium centrifugation in sucrose gradient. Electron microscopy of the 1.23--1.24 g/ml buoyant density fraction revealed particles 60--80 nm in diameter showing morphology characteristic of oncornavirus A. Isoelectric focusing in polyacrylamide gel showed polypeptides of extracellular D virus and oncornavirus A to differ in isofocusing points (pI). Proteins of extracellular D virus were localized in zones with pH 3.7, 4.0, 4.4, 4.7, 5.6, 6.5, 8.1, 9.45, and 10.0; polypeptide of intracytoplasmic oncornavirus A had the following isofocusing points: 4.0, 4.9, 6.7, 7.3, 9.0, 9.45 and over 10.0. Electrophoresis of polypeptides of D virus and intracellular oncornavirus A revealed differences in the molecular weights of the components. No proteins with molecular weights of 10,000, 12,000, 15,000, and 27,000 dalton characteristic of the extracellular D virus were found in oncornavirus A virions. The analysis of protein patterns obtained in parallel experiments of isoelectric focusing and polyacrylamide gel electrophoresis suggests that oncornaviruses A and D of J-96 cells differ in the characteristics (pI and molecular weight) of the structural polypeptide components.

Electron microscopy and biophysical methods were used for examinations of primarily trypsinized chick fibroblast cell culture spontaneously producing C-type oncornavirus at 1, 6, and 24 hours after inoculation with Sindbis virus. During the first 6 hours rapid maturation and release of oncornavirus from cells were observed. At later intervals oncornavirus production was inhibited. It is assumed that in the system under study, biosynthesis of oncornavirus and Sindbis virus occur separately.

Data on structural organization and interactions inside the virion of bovine leukemia virus (BLV) proteins are presented. Uniqueness of the structural organization of BLV proteins having no antigenic relationship between the corresponding animal retrovirus proteins is emphasized. Certain connection is also observed in the structural organization of surface glycoprotein gp69, major internal protein p24 and internal protein p12 with the corresponding polypeptides of human T-cell leukemia virus (HTLV). It is shown that BLV proteins form various complexes inside the virion which are not found in other known retroviruses. A structural model of BLV is presented.

Virions of types B and C similar to previously known mammal oncornaviruses were found in tissue cultures prepared from epithelial cells sedimented from the milk of a lactating woman with mammary cancer (HEC-31) and the milk of two clinically normal women (HEC-33 and HEC-34). In HEC-33 culture type C particles were predominant quantitatively. All the three milk specimens gave an identical precipitation line with antiserum for the milk of the mammary cancer patient as well as sequences forming molecular hybrids with DNA product of oncornavirus type D. At the same time, no positive immunologic reaction was obtained with the test system for oncornavirus type D from HEp-2 cells.