At the time of the original study (end of last century), the phys

At the time of the original study (end of last century), the physico-chemical characterization of particles, in this case nanoscale particles in an aqueous suspension, was generally poor. Data

on hydrodynamic particle diameters or ζ potential are thus missing. Nevertheless, the approach already aimed to achieve an effective dispersion of particles in saline by stirring. Being aware of the agglomeration problem with click here nanoscale particles an ultrasonic treatment of 10–30 s was included. Based on today’s knowledge and the dispersion characterization, the dispersions will have had mean agglomerate sizes of about 300–500 nm. For details on treatment groups, numbers of investigated animals, and dosing regimes, see Table 2. Animals were exposed to the particle suspensions by intratracheal instillation. Due to the completely different focus of the original study, however, aimed at inducing comparable grades of chronic inflammation for all three granular

dusts, mass doses of the three particle types in the subacute, subchronic and chronic study parts were not identical (see Table 2). The administered mass doses thus depended on known particle characteristics. Quartz DQ12 (highly reactive crystalline silica, triggering progressive lung injury) and Printex® 90 (carbon black) are poorly soluble dusts, whereas amorphous silica (Aerosil® 150) is a non-biopersistent dust that is eliminated relatively fast (half-life in rats approx. 1 day; rat study by Fraunhofer ITEM, 1999) and triggers acute toxicity but only temporary inflammation in the lung. Printex® 90-treated animals Isotretinoin received three times higher particle mass doses in the 3-month study part than silica-treated animals

(quartz DQ12 and Aerosil® 150). Consequently, correlations regarding expression of the genotoxicity markers between Printex® 90-treated animals and animals treated with the other particle materials were limited. However, quartz DQ12 and Aerosil® 150 were instilled at the same doses and intervals, thus enabling material-based direct comparison of the data. As the ratios of doses of the different dusts also varied between the 3-month and lifetime study parts, correlations of genotoxicity marker expression and tumor data could be evaluated only with certain restrictions. For immunohistochemical detection of the chosen genotoxicity markers in lung tissue, 3-μm paraffin sections were cut from the lung material, using one block of the left lung lobe for each animal, and were mounted on glass slides. Paraffin sections were then dewaxed and subject to DNA hydrolysis with 4 N HCl and the corresponding antigen retrieval methods, which had been validated for each of the primary antibodies. The primary antibodies used comprised protein A column-purified mouse monoclonal antibody 10 H (generous gift from Prof. A.

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