Three cases of infantile digital fibromatosis were studied by electron microscopy, enzyme histochemistry, and tissue culture. The tumors were made up equally of myofibroblasts containing electron-dense inclusions which were composed chiefly of microfilaments measuring about 5 to 7 nm. Dense bodies usually observable in the smooth muscle cells were found in the bundles of these microfilaments and in the process of the inclusions, suggesting that these inclusions may represent an abnormal accumulation of contractile protein in the cytoplasm of tumor cells. Two cell lines were established from culture of the tumor cells, and the cultured cells also contained inclusion bodies showing the same morphologic characteristics as those of the original tumor cells. Lysosomal enzymes were abundant in the cultured cells, but they were scant in the cells of the fresh tissue specimens. Cocultivation of the cultured cells with human embryonic lung cells yielded no cytopathic effect.
SUMMARYIn order to investigate the nature of tubular structures specifically found in herpes simplex virus type 2 (HSV-2)-infected cells, the multiplication of HSV-2 was studied in Veto cells cultured in the presence of varying concentrations of cytosine arabinoside (Ara-C) and cycloheximide (CH), inhibitors of DNA synthesis and protein synthesis respectively. Ara-C, at a concentration of6o/zg/ml, inhibited the multiplication of HSV-2 by more than 99 % and also prevented the appearance of tubular structures and virus particles in the nuclei of infected cells. Nevertheless, the synthesis of virus specific surface antigens of HSV-2-infected Vero cells was not reduced, as revealed by the fluorescent antibody technique. On the other hand, IO/zg/ml of CH inhibited both the appearance of tubular structures and virus particles and the synthesis of virus specific surface antigens by more than 99 %. These observations strongly suggest that the appearance of tubular structures is one of the late events in the process of virus multiplication.To measure the comparative genome size needed to produce membrane antigens, tubular structures and infectious centres, the effect of u.v.-inactivation of HSV-2 on these processes was studied. After u.v.-irradiation, the capacity to induce tubular structures was inactivated at a slower rate than the capacity to form infectious centres, but at a faster rate than the induction of surface antigens. Furthermore, more tubular structures could be induced by u.v.-inactivated virus than by the nonirradiated virus which was diluted to the same infectivity as the u.v.-irradiated virus. These results indicate that expression of the entire genome is not required for the production of tubular structures.
Two cell cultures were obtained from excised tumors of two cases of infantile digital fibromatosis (IDF). The cells had eosinophilic cytoplasmic inclusion bodies characteristic of IDF. Although the rate of cells bearing the inclusion bodies was high at the earlier passage levels, it was reduced to zero by the 15th passage of one of the cultures, but the cells of the other culture continued to produce the inclusion bodies even at the 30th passage. Chromosome analysis revealed both cultures to have tetraploid cells in approximately 8 to 12% in late passage levels. No viruslike particles were found in electron microscopy. No tumors developed when the cells were inoculated into athymic, nude mice subcutaneously. These cell cultures will be valuable for characterizing the eosinophilic inclusion bodies and determining the origin of the tumors.
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