Fig. 1.

The cell-block sections of MeT5A cells with uptake of crocidolite fibers. Images were taken at ×1000 magnification (oil-immersion). (A, B, C and D) MeT5A cells at 70% confluence were incubated with 5 µg/cm² crocidolite for 2 h. (E and F) MeT5A cells without crocidolite. Compared with routine HE staining (A), crocidolite fibers can be identified more easily by Kernechtrot staining (B) in bright field observation. By observing the same area of the sample with Kernechtrot staining, crocidolite fibers contrasted better in dark field observation (C), but for identification and counting of intracellular fibers, dark field observation appeared not to have enough advantage even by using unstained sections (D), partly because MeT5Acells themselves without crocidolite fibers showed focal brightness, especially nearby plasma membrane both in the unstained section (E) and in the section with Kernechtrot staining (F).