Loosening of Condensed Chromatin in Human Blood Lymphocytes Exposed to Irradiation with a Low-Energy He-Ne Laser

摘要

It was shown that, 1 h after irradiation of human blood lymphocytes with a He-Ne laser at 56 J/m~2 (5.6 W/m~2, 10 sec), the relative optical density of condensed chromatin masses observed in ultrathin sections was decreased (p < 0.01); i.e., the condensed chromatin became less compact. Such transition of condensed chromatin to a more "open" state may improve its availability for regulatory proteins and transcriptional factors. The irradiation also results in dispersion of condensed chromatin clumps in the nuclcoplasm and enhancement of their angularity, i.e., in extension of the clump surface. These shifts, correlating with the activation of transcription, may be due to decompaction of the chromatin fibers not only on the periphery of chromatin clusters in the center of the nucleus, but also within the masses of condensed chromatin.