[Ultrastructure of glioma vessel--morphometric study for vascular permeability]

In this study we investigated the ultrastructure of human glioma capillaries in operated sample of low grade astrocytomas and malignant gliomas. Electronmicrographs of a total of 58 vessels were analyzed with computer assisted morphometry for ultrastructural evidence of permeability routes. All of these vessels were present in the marginal area of tumors devoid of necrosis, less than 10 micron in diameter and containing one nucleus at least on axial section. We found that: (1) The number of pinocytic vesicles was significantly higher in capillaries from malignant glioma (an average of 8.1 per 1 micron (2) cytoplasm) than those from low grade astrocytoma (an average of 4.0 per 1 micron (2) cytoplasm). In capillaries from malignant glioma, most of the pinocytic vesicles were arranged in the abluminal side of endothelium and some of them were fused each other. (2) Abnormal endothelial intercellular junctions which were defined as short tight junctions (less than or equal to 0.25 microns) were equally but infrequently seen in low grade astrocytomas and malignant gliomas. (3) Fenestrations in the endothelium were not seen. Therefore we suggest that the high vascular permeability and resultant brain edema in malignant gliomas is likely to increased pinocytic vesicles and rare but abnormal inter endothelial junctions.