Fig. 3

Uptake of composite dusts by NR8383 macrophages in F-12 K medium. All photomicrographs were taken after 16 h in culture. a and b represent light microscopic images, while c, d, e and f are transmission electron microscopic images. a: particles settled under cell-free culture conditions at the bottom of the culture vessel. Here GrandiO is shown, but the observations for the other particles were very similar. b: The sedimented particles as shown in a have been taken up by macrophages. Note that the space between the cells has been cleared from particles and most macrophages appear dark due to particle uptake, indicating that the macrophages have ingested the entire dose. The observations for the other composites were very similar. c, d, e and f: Transmission electron microscopy indeed confirmed that the particles were phagocytized by the macrophages. c and e: Macrophages on the aclar film (A). In the cytoplasm, vesicles, vacuolae, mitochondriae and endoplasmatic reticulum can be discerned. Also several phagosomes with internalized composite dust particles can be observed (black arrows) in the cytoplasm. d and f show a detail of c and e, illustrating the engulfed particles in the phagosomes. Dust particles containing nano-sized filler particles can be observed, but also large silicate glass particles have been taken up. As cutting these glass particles by ultramicrotomy is difficult (even with a diamond knife), this often results in artifacts due to particles that have fallen out of the section (white arrows). The membrane of the phagosomes can clearly be recognized