The morphology of experimental tumours of the nervous system. II. Intracerebral tumours in the rat

Tumorigenic clones of hamster brain cells transformed in vitro by polyoma virus. Ultrastructural and immunohistochemical study

The morphological characteristics of three clones of hamster brain cells transformed in vitro by polyoma virus and of the tumors obtained after subcutaneous grafting of these cells in syngenic animals are reported. These clones appeared to be glial in nature by light and electron microscopy. The initial tumors induced by the three clones presented astrocytic features both by electron microscopy and immunohistochemistry. Analysis of the subsequent in vivo passages showed a decrease in cell differentiation, which was accompanied by a decrease in the latency period; after 2 years of serial transplantation, the tumors seemed poorly differentiated gliomas. A control cell line of hamster cerebellar cells evolved similarly.

Differential morphological reaction of experimental CNS tumour clones in vitro to dibutyryl cyclic AMP or serum-free medium, resp

Six clones from methylnitrosourea (MNU) or ethylnitrosourea (ENU) induced tumours obtained in the nervous system of the rat were cultured in serum-free medium or treated with dibutyryl cyclic AMP (db cAMP) in vitro. All clones originated from longterm cultures. Three clones forming sarcomas after syngeneic transplantation showed only very slight changes following treatment, whereas the three glioma clones showed striking alterations. They formed long processes or showed rounding of their perikarya. In serum-free medium the cellular shape is intermediate between that seen in normal conditions and the seen in db cAMP treated cultures. The altered cultures resemble the primary cultures of the respective tumours. The relationship of these alterations to tumour types are discussed.