Incidence of micronuclei in cytokinesis-blocked lymphocytes of medical personnel occupationally exposed to ultrasound

In order to investigate possible DNA damaging effects of ultrasound, the mi cronucleus assay on cytokinesis blocked human lymphocytes was performed. Pr eparations were stained by conventional Giemsa staining technique combined with additional staining techniques using fluorescent dye DAPI and silver n itrate. Blood samples were taken from medical personnel employed on ultraso nic scanning in medical diagnosis and unexposed control subjects from gener al population. Lymphocytes were cultivated ir? vitro at 37 degrees C. Cytoc halasin-B in final concentration of 6 mu g/ml was added 44 h after mitogen stimulation and cultures were harvested 28 h thereafter. Staining with both additional techniques can be used to distinguish micronuclei originating f rom breakage or mitotic loss of certain human chromosomes bearing DAPI-posi tively stained or silver-positively stained regions. The results obtained i ndicate: statistically significant increases in total number of micronuclei and changes in their distribution in exposed subjects compared to control. Based on different intensity of DAPI staining signal-positive and signal-n egative "type" of micronuclei are distinguished while silver staining has r evealed Ag-NOR+ and Ag-NOR- micronuclei. In exposed subjects a prevalence i n number of Ag-NOR+ micronuclei over Ag-NOR- micronuclei compared to contro l was observed, indicating greater susceptibility of chromosomes from D and G groups to damage caused by continuous occupationally exposure to ultraso und. Tn spite of their limitations, our results indicate that combination o f conventional Giemsa staining of micronuclei with fluorescent dye DAPI and silver nitrate staining techniques can be valuable complement to the stand ard micronucleus assay.