A novel nucleolar biomarker in plant and animal cells for assessment of substance cytotoxicity

The cytotoxicity of three substances (mercury(II), metolachlor, and 4-nitroquinoline-N-oxide) was assessed with a set of nucleolar parameters: the average number of nucleoli, the average volume of a single nucleolus, and the proportion of cells with heteromorphic-paired nucleoli (PNhet). Their toxic impact was studied on cells of animal and plant test organisms: onion (Allium cepa), lettuce (Lactuca sativa), and hydra (Hydra attenuata). In general, at concentrations near IC/LC50 the three chemicals produced similar cytogenetic effects after 30-360 min of contact. For instance, in plant cells (Allium cepa and Lactuca sativa) the toxicants increased the percentage of cells with PNhet, decreased the volume of single nucleoli, and exerted no significant impact on the nucleolar number. In animal cells (Hydra attenuata), they reduced the size of nucleoli, produced no effect on the number of nucleoli, but decreased the share of cells with PNhet. Also, the chemicals affected the cells of the three test organisms to different degrees. Thus, the effectiveness of our approach of using nucleolar biomarker (use of the proposed set of parameters and time schedule of several determinations in the first hours of toxicant contact, etc.) as a means of assessing cytotoxicity was confirmed. (C) 2002 Wiley Periodicals, Inc.