['Page', '17', 'collected.', 'Microscopic', 'evaluation', 'of', 'Pappenheim-stained', '(Romeis,', '1968)', 'smears', 'of', 'bronchoalveolar', 'lavage', 'cells', 'confirmed', 'the', 'flow', 'cytometric', 'results.', 'An', 'aliquot', 'of', 'the', 'above', 'fixed', 'lavaged', 'cells', 'was', 'analyzed', 'for', 'spontaneous', 'fluorescence.', 'The', 'system', 'was', 'internally', 'calibrated', 'by', 'adding', 'monodisperse', '(diameter:', '1.95', 'jum)', 'fluorescent', 'latex', 'beads', '(Duke', 'Scientific,', 'Palo', 'Alto,', 'CA)', 'into', 'the', 'cell', 'suspension.', 'After', 'gating', 'the', 'AM', 'population', 'from', 'a', 'dot', 'plot', 'histogram', 'of', 'axial', 'light', 'loss', 'vs.', 'right', 'angle', 'light', 'scatter,', 'the', 'green', 'fluorescence.', '(515', '-', '530', 'nm)', 'was', 'quantified', 'in', 'arbitrary', 'units', 'normalized', 'to', 'that', 'of', 'the', 'admixed', 'latex', 'beads.', 'From', 'each', 'sample,', '15,000', 'counts', 'were', 'collected.', ':', '8-Hydroxy-Deoxyguanosine', 'Determination', 'As', 'a', 'measure', 'for', 'possible', 'oxidative', 'DNA', 'damage,', '8-OHdG', 'was', 'determined', 'in', '&', 'rats/group', 'after', '6', '(WBO', 'and', 'WB12', 'only)', 'and', '12', 'months', '(all', 'groups)', 'of', 'inhalation.', 'During', 'the', 'last', 'exposure', 'day,', 'rats', 'were', 'killed', 'as', 'described.', 'The', 'lungs', 'were', 'perfused', 'in', 'situ', 'with', 'isotonic', 'saline', 'to', 'remove', 'erythrocytes.', 'The', 'lungs', 'as', 'well', 'as', 'the', 'nasal', 'respiratory', 'epithelium', 'and', 'the', 'nasal', 'olfactory', 'epithelium', 'were', 'stored', 'frozen', 'at', '-70°C', 'until', 'further', 'processing.', 'DNA', 'extraction', 'was', 'performed', 'according', 'to', 'Gupta', '(1984)', 'with', 'emphasis', 'on', 'fast', 'tissue', 'processing', 'to', 'prevent', 'both', 'DNA', 'repair', 'and', 'artificial', 'DNA', 'oxidation.', 'Enzymatic', 'digestion', 'of', 'DNA', 'as', 'well', 'as', 'chromatographic', 'separation', '(Nucleosil', '100-5', 'C18', 'precolumn,', 'CS', 'Chromatographie', 'Service,', 'Langerwehe,', 'Germany;', 'Novapack', 'C18,', 'Waters', 'Millipore;', 'HPLC', 'HP', '1050,', 'Hewlett', 'Packard)', 'and', 'electrochemical', 'determination', '(HP', '1049A,', 'Hewlett', 'Packard)', 'of', '8-OHdG', 'were', 'performed', 'according', 'to', 'Shigenaga', 'et', 'al.', '(1990).', 'The', 'amount', 'of', 'deoxyguanosine', '(dG)', 'present', 'in', 'the', 'samples', 'was', 'determined', 'by', 'its', 'absorbance', 'at', '245', 'nm.', 'ST@plisosz', ' ']