Mitotic figures and pyknotic nuclei and necrotic cells in the mouse jejunum during injury and repair after whole-body gamma irradiation.

Radiation induced changes in the crypts of jejunum were studied in adult Swiss albino mice exposed to 4.5 Gy, 9.0 Gy and 12.0 Gy of 60Co gamma rays. Two parameters--mitotic figures and pyknotic nuclei and necrotic cells were studied quantitatively to assess the radiation damage and subsequent recovery. Their number in the crypt section was counted at 6 hours, 1, 2, 4, 6, 8 and 14 days after irradiation. In all the three exposure groups the minimum value for mitotic figures was obtained on day 1 when the pyknotic nuclei and necrotic cells were highest. On day 2 partial recovery was seen in both the parameters studied and by day 8 in mice exposed to 4.5 Gy and by day 14 in mice exposed to 9.0 Gy and recovery was complete. However, in mice exposed to 12.0 Gy no mice survived till the last autopsy interval and the normal values were never attained.