New articles published: V. 14 n. 4 (2026)

Effects of Colcemid on Mitotic Index and Metaphase Quality for Cytogenetic Dosimetry

Abstract: Cytogenetic dosimetry plays an important role in assessing individual exposure to ionizing radiation, especially through analysis of dicentric chromosomes (DC). For DC assessment, peripheral blood lymphocytes are mitogen-stimulated and cultured with Colcemid added to arrest cells at metaphase for chromosome analysis. This study evaluated how Colcemid concentration and the timing of its addition to the culture affected the mitotic index (MI), the frequency of first-division metaphases (FM1), and the quality of chromosomal contraction for microscopic analysis. Peripheral blood samples from two volunteers were irradiated with 6 Gy and cultured for 72 hours with different concentrations of Colcemid (0.05 and 0.10 μg/mL), added at 0, 24, and 45 h. In irradiated samples, early addition (0 h) of 0.05 μg/mL Colcemid yielded the most favorable balance, with higher MI values (≈ 9 %) than samples treated with 0.10 μg/mL, while maintaining FM1 > 90 % and adequate chromosomal contraction. An explicit MI × FM1 trade-off emerged: the higher concentration maximized the first-division fraction (FM1 ≥ 99 %), the endpoint that directly conditions dicentric scoring, but reduced the MI of irradiated cultures (6.8 % vs 9.0 %), whereas the lower concentration preserved mitotic progression at the cost of a modestly lower FM1 (≈ 94 %). Delayed addition (24 and 45 h) improved no endpoint and further reduced the first-division yield. These findings show that Colcemid optimization requires balancing mitotic yield against first-division predominance, given the combined cytotoxic effects of Colcemid and ionizing radiation, which directly influence the accuracy and efficiency of dosimetric assessment across different exposure situations. Read full article.