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LIFE01200604005 Shri Somnath Ghosh - Homi Bhabha National ...

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SYNOPSIS<br />

Fig. 3.4G Gene expression of NF-kB (p65) and iNOS gene in EL-4 cells which had<br />

received medium from irradiated cells. EL-4 cells cultured for 2 h in presence of different<br />

conditioned media. Key: Lane 1, control EL-4 cells; Lane 2, γ irradiated EL-4 cells;<br />

Lane 3, EL-4 cells receiving medium from γ irradiated EL-4 cells; Lane 4, EL-4 cells<br />

receiving medium from L-NAME treated and γ irradiated EL-4 cells; Lane 5, EL-4 cells<br />

receiving medium from cPTIO treated and γ irradiated EL-4 cells; Lane 6, EL-4 cells<br />

receiving medium from LPS-stimulated (500ng/ml), L-NAME treated and γ irradiated<br />

RAW 264.7 cells; Lane 7, EL-4 cells receiving medium from LPS-stimulated<br />

(500ng/ml), cPTIO treated and γ irradiated RAW 264.7 cells. Data represents means ± SE<br />

of three independent experiments; significantly different from unirradiated controls: *P <<br />

0.05, **P < 0.01.<br />

CHAPTER 4: DISCUSSION<br />

The work embodied in this thesis clearly shows that the fractionated doses led to a<br />

signaling response that was different from a single dose of irradiation. The work also<br />

stresses on the signaling differences between Low and High LET radiation and the fine<br />

tuning of bystander signaling. The observed results have been extensively discussed in<br />

this chapter and their significance and impact has been discussed in context with the<br />

current literature. The conclusions drawn from this study has also been included in this<br />

chapter.<br />

4.1 Fractionated irradiation induced signaling and repair in mammalian cells.<br />

In tumor radiotherapy, radiation is given as fractionated doses [4]. This leads to<br />

development of radioresistance in the surviving tumor cells. Chronic exposure of cells to<br />

ionizing radiation induces an adaptive response that results in the increased tolerance to<br />

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