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Among 28 strains of influenza A (H3N2) virus isolated from human patients 3 strains were found to be capable of replication in continuous monkey kidney cell cultures. When cells of different origins (PPO, chick embryo chorioallantio membrane, human nasal mucosa) were infected with the virus or when PPO were infected with allantoic or cultural virus strains, the pathological changes were of the same type. No specific inclusions were found in the cells. Adaptation of the virus to PPO cells resulted in inhibition of its hemagglutinating, neuraminidase and interferon-inducing activity and in decrease of thermostability, but the infectious and antgenic properties were retained unchanged.

Comparative characteristics of cytopathic changes in the cell cultures infected with adenovirus and with a biologically active preparation of adenovirus DNA are presented. The pathological process in the cells infected with the infectious DNA differs from that after virus infection by a shortened time of DNA penetration into the cell and a shortened latent period of infection development. The development of the pathological process in the cell cultures was accompanied by a complex of cytological changes with predominant affection of the nuclei and formation of intranuclear inclusions staining green with acridine orange. The distinctive feature of these changes was the time of their appearance: in cultures infected with the virus inclusions were formed within 12-48 hours, in those infected with DNA within 9-18 hours. The fluorescent antibdoy procedure revealed a virus antigen in these cultures induced by DNA preparationand by the virus, at different stages of its accumulation. The nucleoplasm was the site of specific antigens synthesis. The distribution of the virus antigen in the infected cells corresponds to the morphological pictures of intranuclear inclusions at later stages of infection which confirms the viral nature of the latter. The dynamics of the development of cytological changes and intranuclear inclusions in the infected cells as well as synthesis of a specific antigen in them are directly related to the quantitative accumulation of the virus.

A virus-carrier state was observed in the process of subcultivation of foot-and-mouth disease virus-infected calf kidney cell culture. Cytologically, the chronically infected culture differed from the control culture by the presence of a large number of syncytial cells which did not die in acute infection because of poor susceptibility to the virus. Chronic infection appeared to be maintained by occasionaly polygonal cells which retained the initial sesceptiblity to foot-and-mouth disease virus. The number of such cells did not exceed 1--4% and by the 9th passage they disappeared completely. At this time the experimental culture did not differ from control cytologically and cytochemically.

The paper is concerned with comparative cytogenetic studies of human cell line J-96 and subline J-41 derived from it. Application of G-, R- and C-techniques for differential staining of chromosomes made it possible to determine both numeric and structural changes in chromosomes of the resistant subline as compared to the initial one. The mechanisms contributing to a decrease in the normal chromosome number and to appearance of new marker chromosomes in the resistant subline cells are discussed as well as the possible relation of the found chromosome changes to the loss of cell sensitivity to the Coxsackie B3 virus.