Measurement of micronuclei in lymphocytes

Introduction:
This text is a scientific article published in Mutation Research in 1985, which presents two methods for measuring micronuclei in lymphocytes as a method for assessing chromosomal damage. The authors developed these methods to identify cells that have undergone their first mitosis to overcome the imprecision of the conventional micronucleus technique.

Key Points:

* The authors developed two methods to identify cells that have undergone their first mitosis: an autoradiographic technique and a cytokinesis-block method.
* The autoradiographic technique involves pulse-labeling lymphocytes with [3h]thymidine at 48 hours of culture, allowing them to proceed through mitosis, identifying them between 72 and 84 hours, and scoring micronuclei in them.
* however, the autoradiographic technique was not useful for measuring pre-existing chromosomal damage present in vivo due to the production of micronuclei by the radiolabel itself.
* The cytokinesis-block method involves adding cytochalasin B to inhibit cytokinesis and scoring micronuclei in cytokinesis-blocked cells, which are easily recognizable by their binucleate appearance.
* The cytokinesis-block method was simple to perform, quantitated micronuclei produced by irradiation of lymphocytes in vitro, and did not produce micronuclei itself.
* The authors found that the cytokinesis-block method was the procedure of choice for quantitating micronuclei in lymphocytes.

Main Message:
The text highlights the importance of developing reliable techniques for biological dosimetry of exposure to radiation or other forms of genotoxic agents. The micronucleus method has the potential for becoming such a technique since measurement of the baseline number of micronuclei is simple and rapid. however, the establishment of base-line levels and induced levels of micronuclei cannot be performed until the kinetic problem of micronucleus expression is recognized. The cytokinesis-block method appears to be the superior method for quantitating micronuclei in lymphocytes, providing increased precision in the final estimate and enabling both the measurement of the baseline level of micronuclei, which reflects in vivo chromosomal damage, and comparisons of mutagen-induced micronuclei in individuals whose lymphocytes might respond differently to Pha. Overall, the text emphasizes the importance of developing accurate and reliable techniques for measuring chromosomal damage to assess the risk of genotoxic agents.

Fenech, Michael, and alexander a. Morley. “Measurement of Micronuclei in Lymphocytes.” Mutation Research/Environmental Mutagenesis and Related Subjects 147, no. 1–2 (February 1985): 29–36. https://doi.org/10.1016/0165-1161(85)90015-9.