Micronuclei and Other Nuclear Anomalies in Buccal Smears: A Field Test in Snuff Users

Abstract

A revised protocol for the exfoliated cell micronucleus assay was field-tested in a population exposed to a genotoxic agent, snuff, at levels associated with a significant increase in cancer risk. The standard assay involves examination of epithelial smears to determine the prevalence of micronucleated cells, an indication of chromosome breakage or mitotic interference. The assay was revised to increase specificity and to include separate scoring of other nuclear anomalies associated with cytotoxicity and genotoxicity. The modified assay was applied to buccal smears of 38 female snuff users and 15 female nonusers recruited from a North Carolina clinic in 1987. The prevalence of micronucleation was elevated in the snuff users as compared with the nonusers (prevalence ratio = 2.4, 95% confidence interval 1.1-5.2) and, to a lesser extent, at the usual contact site as compared with a distal buccal site in the snuff users (prevalence ratio = 1.5, 95% confidence interval 0.9-2.5). The pattern of relative frequencies of several nuclear anomalies provided strong evidence of a cytotoxic effect, the prevalence ratios ranging from 2 to 13. Nuclear degenerative phenomena can be difficult to distinguish from classical micronuclei; thus, the observed association of indicators of cytotoxicity with exposure introduces the possibility of bias away from the null in micronucleus findings due to differential misclassification. Until methods to better distinguish extranuclear bodies of different origins become available, investigators should use the revised protocol and should focus on agents not thought to be cytotoxic.

Exposure of thermoelectric power-plant workers to volatile organic compounds from fuel oil: Genotoxic and cytotoxic effects in buccal epithelial cells

“…The cells were smeared onto pre-cleaned glass slides. After air-drying, cells were fixed in methanol for 20 min at 0 • C, and the Feulgen method, modified from Tolbert et al [12,14], was applied for staining. Feulgen-stained slides were evaluated under a light microscope with 1000× magnification, using immersion oil.…”

“…Micronuclei in exfoliated buccal epithelial cells emerge during mitosis of the basal layers of the epithelium as extra-chromosomal DNA particles, when chromosome fragments or whole chromosomes lag behind and fail to be included in the main nuclei of the daughter cells, as a result of a clastogenic or aneugenic events [11,12]. Micronuclei in epithelial cells reflect genotoxic events occurring in the dividing basal cell layer of the putative target organ 1-3 weeks earlier [13,14], which allows for cytogenetic surveillance of groups at high risk of developing organ-specific cancer (e.g., upper aerodigestive tract) or oral premalignant lesions [15][16][17]. Chromosomal damage in epithelial cells also leads to nuclear anomalies other than micronuclei, such as karyorrhexis, karyolysis, pyknosis, condensed chromatin, 'broken eggs' and bi-nucleated cells [11,18].…”

“…Chromosomal damage in epithelial cells also leads to nuclear anomalies other than micronuclei, such as karyorrhexis, karyolysis, pyknosis, condensed chromatin, 'broken eggs' and bi-nucleated cells [11,18]. Karyorrhexis, karyolysis and pyknosis are associated with both cytotoxicity (necrosis and keratinization) and genotoxicity (apoptosis) accompanying the early stages of apoptosis [12,14], and thus are also considered effective Table 1 Age and main lifestyle habits of the groups exposed (power-plant workers) and non-exposed (administrative workers) to VOCs [data are reported as the number of subjects (% between brackets)]; VOCs concentration (mean ± SD) from both working areas (thermoelectric power-plant facilities and offices of administrative services). biomarkers for populations exposed to mutagenic and carcinogenic agents [19].…”

CYP1A1 Gene Polymorphisms: Modulator of Genetic Damage in Coal-Tar Workers

“…At least 1000 cells were scored for presence of micronuclei in exfoliated buccal cells at 1000 X magnification under bright field microscope. The scoring of micronuclei was done according to criterion of Tolbert et al 1991.…”

Genotoxicity Biomarkers: Application in Histopathology Laboratories

“…All samples were coded and analyzed under blind conditions. The criteria for scoring the nuclear abnormalities in lymphocytes and MN in the buccal cells were the ones described by, respectively, Fenech et al (1999) and Tolbert et al (1991).…”