マウスの脳内毛細血管と血管周囲組織の発生過程における経時的変化に関する研究

STUDY ON THE BRAIN CAPILLARIES AND THEIR SURROUNDING TISSUES AT VARIOUS STAGES OF DEVELOPMENT IN MICE

　抄録　マウスの脳内毛組血管と血管周囲組織の発生過程における経時的変化を，電顕的に検索した。胎齢10日から55日齢のマウスが使用され，胎齢期では，前脳の側方拡張部が，出生後では，頭頂葉皮質深層が検索された。内皮細胞は日齢の経過とともに，その複雑さと厚さを減退させたが，4日齢までの血管では，内皮細胞中にlarge vesicleと多数のpinocytotic vesicleが認められ，脳血管の透過性が大きい事を示唆していた。8日齢で毛細血管の発芽が認められたが，55日齢でも血管腔の著しい狭小と内皮細胞に大型の核を保有する，新生血管同様の形態を示す血管が認められた。基底膜の一部は，出生時にすでに存在していたが，その成熟は血管および周囲組織の発達と著しい関係があった。

　本研究は，異なる透過性を保有するいくつかの毛細血管が，脳内に長期間存在することを明らかにし，このことは，血液脳関門の成立のうえで重要な役割を演ずることを示唆していた。

The development of the brain capillaries and their surrounding tissues from fetuses to adult mice were studied ultrastructurally.

1. The intracerebral blood vessels on day 10 of gestation showed sinusoid characteristics.

2. The interendothelial junctional complex on day 15 of gestation showed the zonula occludens like in the case of adult.

3. The anlage of pericyte was observed already on day 15 of gestation.

4. The endothelium decreased prominently in its complexity and thickness till the 8th day of age.

5. Sprouting of the intracerebral capillaries were observed on the 8th day of age.

6. The BM-material was observed continuously near the corresponding plasma membranes of the endothelium on the first day of age. The perivas-cular clefts surrounding the blood vessels were partly open and had direct contact with the extracellular space till 8 days of age.

7. The large extracellular space which was ob-served from the fetuses to the first day of age became remarkably narrower after 4 days and it was observed that there were interrelations between the development of neuropils and narrowing of the extracellular space. This study shows that several capillaries with different permeabilities coexist over a long period of time in the cereberum. The latter seems to play an important role in the formation of the blood-brain barrier.