組織培養におけるグリア細胞の形態，とくにその変態と増殖について

Transformation and Multiplication of Neuroglia in Tissue Culture

まえがき

　吾々が中枢神経の機能あるいは形態を考えるとき，勿論ニューロンをまず念頭においているわけであり，それは自然なことでもある。しかしその主役を演ずるニューロンにのみ注目して，これの場をつくつている他の細胞要素，特にグリア細胞が余りにも軽視されていはしなかつただろうか．たしかにグリアは，余りにも脚光の集中したニューロンのかげにかくされて来た感がある。

　ニューロンは今日なお多くの謎を秘めている。この未知の分野を研究する義務は吾々に課されてはいるが，ひとたび視角をかえて，その背景をなすグリアに焦点を絞つてみることは，また大いに重要なことではないかと思われる。人間の大脳皮質の全容積のうち、神経細胞が占めるものは僅に2.85％（Bok，′36）にすぎないと云われる。残るものは神経線維と血管および、これに伴う小量の中胚葉性細胞を除けば，グリアであり，その細胞数はおそらくかなり夥しいものになるであろう。とに角，ニューロンに正常の機能を営よせている背後には，グリア細胞の陰の力（しかもそれらの本態はなお不明のままではあるが）が大きいことは想像に難くない。

Neuroglia cells in tissue culture of normal central nervous tissue show:(1) an enormous variety in cell types from fibrous and:or pro-toplasmic astrocytes to flat, unbranched cells, and fu rther to oligodend roglia cells. (2) Another noticeable events are the appearance of multi-nucleate astrocytes and their peculiar cyto-plasmic divisions.

The evidence in both cases could be establ-ished only by following a particular cell and observing its whole process of transformation, multinucleation and cell division.

The present study is concerned with obser-vations revealed by phase contrast time-lapse cinematography of neuroglia after periods of a week to more than a year in culture.

Results : (1) Fibrous and protoplasmic astro-cytes arc transitional. The reversible transform-ation of flat, unbranched cells to protoplasmic and further to fibrous astrocytes has been recorded. Oligodendroglia transformed intosmaller flat, unbranched cells and vice versa. There are no clear boundaries between the latter flat cells and the former except for their difference in size. (2) Multinucleation in astro-cytes resulted from various atypical mitoses which are essentially of two types : a ) Mul-tipolar mitotic nuclear division was followed by cytoplasmic cleavages less in number. b) Daughter cells after an incomplete cell division fused into a giant cell or cells with two or more nuclei. Cine records revealed that small splits between nuclei appeared in the cytoplasm of a multinucleate astrocyte. The splits gradu-ally became prominent and the cell split into three or four mononucleate daughter cells. Sometimes a small cell surrounded by a circum-script space in a larger cell escaped from the latter which was similar to Collin's "end-ocytogenésè".

Factors determining these phenomena were discussed briefly.