Cholesterine granuloma obtained from the mastoid cavities of ten operated patients aged from 12 to 56 years was fixed by Millonig's 1% osmic solution, immediately after removal, embedded in Epon 812, stained by uranyl acetate solution and electron-microscopically observed in order to study the origin of cholesterine crystal which is recognized as cholesterine cleft within the granuloma.
Results obtained were as follows:
1. Small cholesterine clefts (possibly in early stage of development) were seen to be surrounded by numerous degenerated erythrocytes, D-Cell (see below) and phagocytes being in a close contact with each other (Fig. 6, 7).
Several phagocytes in which phagosome, residual bodies and myelin figures indicated their active function, including the small cleft also (Fig. 6, 7).
2. Foam cells contain various sized and forms of vacuoles and granules were often seen around the clefts. Some of the cells contained small cholesterine clefts or phagosomes in the cytoplasma. These cells were therefore, supposed to belong to phagocytes (Fig. 1, 2).
3. Erythrocytes and degenerated cells were always found to be in a close contact with cholesterine cleft at its surface. The former degenerated frequently. The size of the latter was equal to that of the former. It had a cell membrane, but lacked nucleus. The cytoplasma consisted of diffusely scattered fine granules of low electron density.
The feature of the cell suggested that the degenerated blood cell was its origin. Thus the cell was called D-cell by the author.
4. Vascular lesions, such as stasis and thrombosis were frequently observed in the vicinity of the clefts (Fig. 4).
5. These findings strongly suggested that the chole-sterine crystal derived from blood-element which had emigrated from disturbed blood vessels and could develop within extracellular spaces and that it could grow within phagocytes.
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