QUANTIFICATION OF EPITHELIAL-CELL MICRONUCLEI BY FLUORESCENCE IN-SITUHYBRIDIZATION (FISH) IN MORTUARY SCIENCE STUDENTS EXPOSED TO FORMALDEHYDE

A micronucleus assay employing fluorescence in situ hybridization (FIS H) with a centromeric probe was used on specimens of exfoliated buccal and nasal cells collected from mortuary science students exposed to e mbalming fluid containing formaldehyde. FISH labeling allowed micronuc lei (MN) containing a whole chromosome (centromere-positive, MN(+)) to be differentiated from those containing only chromosomal fragments (c entromere-negative, MN(-)). Each student was sampled before and after the 90 day embalming class. We determined if an increase in MN frequen cy could be attributed to formaldehyde exposure and was specific to ei ther MN(+) or MN(-). In buccal cells, total MN frequency was significa ntly increased from 0.6/1000 to 2/1000 (p = 0.007) following the cours e, whereas in nasal cells it was not (2 and 2.5/1000, respectively, p = 0.2). Cells with multiple MN were present only in samples taken afte r exposure to embalming fluid. Although the baseline frequency was hig her for MN(+) in both buccal (0.4/1000 for MN(+) and 0.1/1000 for MN(- )) and nasal cells (1.2/1000 for MN(+) and 0.5/1000 for MN(-)), the in crease in MN frequency was greater for MN(-), (9-fold, p = 0.005 for b uccal cells; 2-fold, p = 0.03 for nasal cells) than for MN(+) (> 2-fol d, p = 0.08 for buccal cells; no change, p = 0.31 for nasal cells) in both tissues, Thus, the primary mechanism of micronucleus formation ap peared to be chromosome breakage, This finding is consistent with know n clastogenic properties of formaldehyde, the component of embalming f luid most likely responsible for micronucleus induction.