Short-term tissue culture observations of experimental primary and transplanted nervous system tumors.

Tumors of the central and peripheral nervous system were induced in BD-IX rats and transplanted serially. Both primary and transplanted tumors in different generations were cytologically analyzed, using primary explants in vitro. Four hundred and thirty single tumors were examined in vitro over th period 1969 to 1977, using the following methods: conventional aniline staining, special silver impregnation, supravital observation of cells by phase contrast microscopy, locomotion studies with time-lapse cinematography, and ultrastructural analysis from transmission and scanning electron microscopy. Cells grown in vitro were subdivided into the following groups, according to their morphology: (1) Apolar cells: Round cells only observed in rare tumors of the nasal cavity and sporadically in transplanted neurinomas; they are thought to represent cells from the reticular variant of neurinoma in the latter. (2) Bipolar cells occurred in two forms: As bipolar fibroblasts and as slender bipolar cells observed in explants of malignant neurinomas. The latter cells grow in parallel arrangements; their tentative interpretation as Schwann cells is consistent with their description in human neurilemomas. (3) Semipolar cells with one clear-cut edge and a broad ruffled membrane opposite. They are described as fibroblasts in the course of locomotion. (4) Multipolar cells, observed in several forms in primary and transplanted gliomas exclusively. Variants with long processes were seen in the first passages of intracerebrally transplanted tumors only; in later generations, all cells had short branching processes and little cytoplasm. Conclusions concerning the cytologic derivation of experimental tumors are discussed.