Micronucleus assay in lymphocytes as a tool to biomonitor human exposure to aneuploidogens and clastogens.

Abstract

The analysis of micronuclei (MN) in cultured human lymphocytes is, in principle, able to detect exposure to clastogens and aneuploidogens alike. There is, however, no clear evidence from human biomonitoring studies or animal experiments showing that in vivo exposure of resting lymphocytes to an aneuploidogen could actually be expressed as MN in cultured lymphocytes. In vitro, a pulse treatment of human lymphocytes with vinblastine, an aneuploidogen, did result in MN induction even if performed before mitogen stimulation, although a much more pronounced effect was obtained in actively dividing lymphocyte cultures. On the other hand, it is probable that a considerable portion of "spontaneous" MN contain whole chromosomes, their contribution increasing with age. It also seems that cytochalasin B, used for the identification of second cell cycle interphase cells in the MN assay, is able to slightly increase the level of MN with whole chromosomes. If MN harboring chromosome fragments represent a minority of the total MN frequency, there may be difficulties in detecting a weak effect in this fraction of MN against the background of MN with whole chromosomes. This would reduce the sensitivity of the assay in detecting clastogens, unless MN with whole chromosomes and chromosome fragments are distinguished from each other. That a problem may exist in sensitivity is suggested by the difficulty in demonstrating MN induction by smoking, an exposure capable of inducing chromosome aberrations. The sensitivity of the lymphocyte MN assay could be increased by detecting kinetochore or centromere in MN, or by automation, allowing more cells to be analyzed.ImagesFIGURE 2.

Genetic monitoring of malathion-exposed agricultural workers

“…However, excluding them did not change the results. Other studies in the literature have found mean micronuclei levels in controls in the range of our comparison groups [Norppa et al, 1993;Fenech, 1993].…”

“…Furthermore, studies have shown different results concerning the association of micronuclei levels and demographic or lifestyle variables [da Cruz et al, 1994;DiGiorgio et al, 1994;Yager, 1990b;Norppa et al, 1993]. Thus, some of the important issues still being considered in relation to interpretation of micronuclei levels in population studies include intra-and interindividual variation, effects of cytochalasin B in the assay, and other sources of variability [Norppa et al, 1993;Radack et al, 1995]. Some recent studies that examined multiple biomarkers of effect found micronuclei frequency to be less sensitive than chromosomal aberrations, SCEs, or high frequency of SCEs [Tates et al, 1994;Van Hummelen et al, 1993].…”

Cytogenetic analysis of buccal cells from shoeworkers and pathology and anatomy laboratory workers exposed ton-hexane, toluene, methyl ethyl ketone and formaldehyde

“…Norppa et al (1993) reported an increased MN frequency in the buccal cells of workers in a plywood plant and ®bre glass factory, while no change was observed in lymphocytes. Suruda et al (1993) demonstrated that low level exposure to FA (0.33 p.p.m.)…”

Micronucleus incidence and their chromosomal origin related to therapy in acute lymphoblastic leukemia (ALL) patients: Detection by micronucleus and FISH techniques

“…Micronucleus formation reflects chromosomal abnormalities that originated in the last in vivo division of nucleated cells, which are basically distinguishable by using FISH with chromosome-specific probes. Nevertheless, the conventional micronucleus assay is not able to distinguish between micronuclei arising from these two types of mutagenetic mechanism [7]. This technique also does not require highly specialised staff [8].…”