Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 73-76). / This work explores the effects of low-dose-rate radiation on both the AA8 (wild-type CHO cells) and EM9 (XRCC1 null CHO mutants) cell lines. In particular, this study performed clonogenic survival and growth assays to determine the radiations/ effect on the cells proliferative capacity. It was hypothesized that the XRCC1 null mutants would show greater radiosensitivity during continuous low-dose-rate radiation since the inability to rapidly respond to DNA damage would result in the gradual accumulation of cytotoxic double strand DNA breaks and/or chromosome exchanges/aberrations. The cells were irradiated for 7 days with photons from unencapsulated 241Am plate sources for chronic, low-dose-rate studies, at dose-rates between 1.99 ± .610 x 10-3 cGy/h and 1.23 ± .0325 cGy/h, and irradiated with a Phillips RT250 X-ray machine at 250 kVp and 2.5 Gy/min to doses between 0.02-10 Gy for acute studies. There were significant differences in the growth rates of the unirradiated controls and the irradiated flasks at all dose-rates for both AA8s and EM9s (except for the EM9 9.08 ± .390 x 10-3 cGy/h flask where p<.10). There were also suggestive (p<.20) differences in the clonogenic survival for both cell lines compared to controls with significant (p<.05) differences observed in the EM9 irradiated population at dose-rates of: 6.89 ± .315 x 10-3 cGy/h, 3.30 + .80 x 10-3 cGy/h, and 1.99 + .61 x 10-3 cGy/h. Moreover, there are suggestive (p<.15) trends indicating that XRCC1 deficient cells are more susceptible to chronic low-dose-rate radiation (dose-rates compared were between 1.99 ± .61 x 10-3 cGy/hand 9.08 + .39 x 10-3 cGy/h) as compared with acute exposures at the same dose. / (cont.) Despite some procedural differences with other published works, these results may be evidence of the "inverse dose-rate" effect noted by other authors. / b y Dwight McCoy Chambers. / S.M.
| Identifer | oai:union.ndltd.org:MIT/oai:dspace.mit.edu:1721.1/53285 |
| Date | January 2008 |
| Creators | Chambers, Dwight McCoy |
| Contributors | Jacquelin C. Yanch., Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering., Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering. |
| Publisher | Massachusetts Institute of Technology |
| Source Sets | M.I.T. Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 76 p., application/pdf |
| Rights | M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission., http://dspace.mit.edu/handle/1721.1/7582 |
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