Fig. 4

The ultrastructure of the BBB and BTB in brain metastases. The normal brain of figure A was obtained by the brain tissue of health mouse without injection of tumor cells. The brain metastases were observed on the sixth day after injection of tumor cells. A1–C1 represent enlarged images of the black frame part in A–C. AS astrocyte, TJ tight junction, BM basement membrane, E endothelial cells, F fenestra of the endothelial cell, PV pinocytotic vesicle. The pink line in A1 represents the basement membrane of BBB in normal brain. The blue line in B1 represents the basement membrane of BTB in brain metastases