[Electron microscopic study of natural SiO2 particles and SiO2 particles isolated from rat lung]

Natural SiO2 particles of 0--4, 0--5 and 5--10 micron of size were investigated by the aid of transmission and scanning electron microscope. Silicosis in rats was induced with SiO2 particles of 0--5 micron of size. After 18 month SiO2 was isolated from the silicotic lung and investigated by the aid of transmission and scanning electron microscopy and with electronmicroscopic diffraction technique. Natural and isolated from silcotic lung SiO granules were divided into different groups according to their planimetrycally measured area, and excentricity calculated from their diameter. It was established, that division of silica particles isolated from lungs became different as compared to the natural silica-dust. Among the silicadust isolated from silicotic lungs of rats proportion of finer granules is much higher than in natural silica-dust-fraction. Granules isolated from lung have rounded edges and part of them shows a decrease of electrondensity. Majority of particules of 0,01 micron of size appears to be isolated in the material got from the silicotic lung.