LIFE01200604005 Shri Somnath Ghosh - Homi Bhabha National ...

CHAPTER 3
RESULTS
3.3.1.2 Number of initial γ-H2AX foci formed for both radiation types of radiation.
Since DNA double strand breaks are the primary toxic lesions induced by radiation, the number
of double strand breaks were scored by examining the foci of phosphorylated H2AX in irradiated
cells. After 15 minutes of either radiation, γ-H2AX foci, visualized as bright spots, were present
in all the cells. The average numbers of foci after 15min of 1Gy gamma irradiation were
15.8±4.8, while after 1Gy carbon irradiation the foci were 19±4.7 (Fig.3.3.1.2). Thus unlike the
cell survival, not much difference was observed in number of γ-H2AX foci after irradiation with
equal doses of carbon and gamma. The foci were also counted 4 hours after irradiation. 57% of
gamma irradiated cells still showed γ-H2AX foci and the average foci per cell had reduced to
only 2.9±2.28. Carbon ion irradiated cells also showed a significant reduction in the number of γ-
H2Ax foci (2±2) per cell that were visible in only 22% of cells (Fig. Fig.3.3.1.2A, B). When total
intensity of γ-H2AX rather than the foci was estimated by ImageJ software in the same images, it
corroborated well with the number of γ-H2AX foci in gamma irradiated cells at 15min and 4hr
after irradiation (Fig. Fig.3.3.1.2C). However, in case of carbon irradiation, the total intensity of
γ-H2AX at 4 hours was yet high (Fig.3.3.1.2C).
Since initial response as observed from γ-H2AX foci at 15 minutes was similar with both type of
radiation, irradiation induced foci of downstream signaling components was followed at 4 hours
to highlight the signaling differences at that time period.
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