Ethylnitrosoureaの経胎盤投与による実験的脳腫瘍（第3報）—Autoradiographyによる腫瘍増殖動態について

EXPERIMENTAL BRAIN TUMORS PRODUCED TRANSPLACENTALLY BY ETHYLNITROSOUREA (Ⅲ):AUTORADIOGRAPHIC STUDIES ON THE TUMOR CELL PROLIFERATION

I．はじめに

　これ迄の実験結果から，ENUの経胎盤投与による実験的脳腫瘍の形態学的特徴は，大半がglia系細胞で，中でもOligodendroglioma, Astrocytoma，或いは両者の混合したmixed gliomaが好発することであり，経時的にみると，いわゆるMicrotumorは生後5週齢頃から認められ，その多くがSubependymal layerに発生し，次第に白質内に発育進展していく形態をとるようにみえることであつた。しかしこの経時的観察の中では，個々の腫瘍がどのような増殖態度をとり，実際どのように進展していくかという動的な解析は出来ず，又個々の腫瘍細胞の増殖と分化の関係も不明であつた。そこで，腫瘍細胞動態解析の第一歩として，³H-thymidine Au—toradiographyを用いて検索を行ない，これ迄に報告された実験的脳腫瘍及びヒト悪性脳腫瘍の増殖動態と比較検討した。

The relationship between the histological abnor-mality in the subependymal layer and the formation of the microtumor as well as the cell kinetics of the growing tumor was examined by using ³H-thymidine flash labeling autoradiography in 18 rats cases. At the perinatal stage, many primitive cells in the matrix layer were labeled with ³H-thymidine autoradiography, which means active synthesis of DNA at the same area.

Diffuse uptake of ³H-thymidine was found in one microtumor and 4 small-sized subependymal tumors whose labeling indexes were between 0.1% and 5%. However, among the middle sized tumors and large tumors, tumor cell groups which showed markedly different labeling indexes in the same tumor were seen in 4 cases. In these cases, the labeling index of the subependymal tumor cells which seemed to be ependymoma was calculated between 25% and 35%, and that of the surrounding small round tumor cells which developed in the white matter revealed between 0.1% and 3%. Points to which special attention should be paid are the high uptake ration of ³H-thymidine at the adjacent area of both tumor cells and the smooth morphological shift between the type of tumor cells which seemed as if the subependymal tumor cells were transformed to small round cells. These findings may show the possibility of the trans-formation or the differentiation of the tumor cells during its proliferation.