Irradiation dose response

Approximately 40% of cancer patients receive radiotherapy as some part of their treatment (http //www.cancerhelp.org.uk/help) and radiosensitization may represent the most significant anticancer therapeutic utility of PARP inhibitors. Radioresistance is a major clinical problem and there is good evidence that it is due to a radiation-resistant, growth-arrested cell fraction within a tumour that can reenter the cell proliferation cycle and thereby repopulate the tumour after radiotherapy.In some in vitro radiopotentiation smdies attempts have been made to mimic the clinical situation by measuring recovery from potentially lethal damage (PLD). In in vitro models of PLD recovery, the increased survival of growth-arrested cells is assessed after a recovery period, in comparison with the survival of cells without the recovery period. In other smdies with exponentially growing cells irradiation dose-response curves in the presence and absence of PARP inhibitor have been compared. Alternatively, recovery from... 

In vivo the doses are always not only due to internal alpha but also due to the external gamma irradiation, which must be taken into account, especially in the low dose range. Therefore in vitro experiments with alpha particles of radon daughters at doses comparable to the in vivo investigations have been carried out (0.05 to 3 mGy). The method is described. Preliminary results show similar dose response as at our in vivo studies. 

Kamiguchi Y., and K. Mikamo, Dose Response Relationship for Induction of Structural Chromosome Aberrations in Chinese Hamster Oocytes After X-Irradiation, Mutation Research 103 33-37 (1982). 

A wide diversity of dose-response (incidence) relationships has been observed among the neoplasms induced experimentally by chemicals (Zeise et al., 1987), radiation (UNSCEAR, 1977) or both. Although neoplasms of virtually every type have been induced in one experiment ra- another, not all types of neoplasms are observed in animals of any one species or strain. Under some conditions, moreover, the incidence of certain neoplasms has actually been observed to decrease with increasing dose of whole-body irradiation (see Figure 3.1). 

Kaplan, H.S. and Brown, M.B. (1952). A quantitative dose response study of lymphoid-tumor development in irradiated C57 black mice, J. Natl Cancer Inst. 13,185. 

Jenssen, A.G. Ramel, C. (1976) Dose response at low doses of X-irradiation and MMS on the induction of micronuclei in mouse erythroblasts. Mutat. Res., 41, 311-320... 

In the case of chicken, even at doses down to 1 kGy (Desrosiers and Simic, 1988) and as high as 25 kGy (Dodd et al., 1988), signal response was proportional to dose. The intensity of the signal induced by a given irradiation dose appears to be species dependent, being much lower for fish (Stewart et al., 1991) than chicken (Dodd el al, 1988). 

Stewart, E.M., Stevenson, M.H. and Gray, R. (1992). Detection of irradiation in scampi tails - effects of sample preparation, irradiation dose and storage on ESR response in the cuticle, lnt. J. Food Sci. Technol. 27. 125. 

Shindo, Y. et al., Dose-response effects of acute ultraviolet irradiation on antioxidants and molecular markers of oxidation in murine epidermis and dermis, J. Invest. Dermatol., 102, 470,... 

The results of our two experiments are consistent with these seasonal changes in the availability of light and iron, given the interrelated influences of irradiance and iron availability on phytoplankton growth rate. The data from our laboratory dose-response iron-addition experiment indicate a relatively high iron requirement for colonial Phaeocystis at an irradiance of 20 fiE m 2 s-1, a value that is representative of the mean irradiance in the mixed layer of the southern Ross Sea during early spring (Smith et al. 2000 Smith and van Hilst 2003 Hiscock 2004). At that time, dissolved Fe concentrations are likely to exceed our estimated half-saturation... 

P. antarctica. Towards this goal, we are currently undertaking further dose-response iron-addition experiments with our P. antarctica culture at higher levels of irradiance. 

In the second experiment, mice were irradiated with the highest dose from the dose-response experiment. Concentrations of lipid hydroperoxides and lipophilic antioxidants were measured simultaneously on single skin samples from irradiated and non-irradiated sides of each mouse. The lipid hydroperoxide assay directly measured lipid peroxidation and thus was superior to the TBARS assay, which is indirect. Lipid-peroxyl radicals have been linked to chemically induced cutaneous carcinogenesis [31] as well as to UV-light-induced cutaneous carcinogenesis [32],... 

In cattle, at any LET value, repair is much slower after heavy ion exposure than after x-irradiation. For ions with an LET of less than 10,000 keV/pm more than 90% of the strand breaks induced are repaired within 24 h. At the highest LET value (16,300 keV/pm) no significant repair is observed (Baumstark-Khan et al, 2003). Thus, a steep dose-response effect is seen at higher doses. 

Catena, C., Asprea, L., Carta, S., Tortora, G., Conti, D., Para-sacchi, P., Righi, E. (1997). Dose-response of X-irradiated human and equine lymphocytes. Mutat. Res. 373 9-16. 

The benchmark spectra used to analyze composite /-irradiated DNA spectra are shown in Figs. 1(B) to 1(E). By determining the low-dose yield [G value (pmol/J)] of each radical using dose-response curves, the low-dose composition of the free radical cohort is determined to be G (35 5%), T- (25 5%), C- [C(N3)H ] (25 5%), XN. (15 5%). Scheme 1 presents the structures of the first three radicals. XN. represents a composite spectrum of neutral radicals, which is assumed to originate mostly with the sugar-phosphate backbone (Cl, C3, C5, C3 gpj J. A semi-quantitative analysis indicates that, of the 15% of assumed backbone radicals, about 11% originate with electron loss and about 4% with low-energy electrons (Sec. 3.3). Thus, about 46% of the stabilized radicals at 77 K are electron-loss... 

A collimated beam test is carried out to determine the UV microorganism s dose-response. The UV intensity (incident irradiance) of 1.00 mW/cm is measured using a radiometer. A 25-mL microbial suspension is irradiated for 60 s in a Petri dish. The irradiation time is monitored using a stopwatch. The Petri dish radius, measured using a ruler with 1 mm graduations, is 2.5 cm. The stir bar volume is 1 mL. The UV decadic absorption coefficient ( jq) of the microbial suspension for a 1-cm path length at 254 ran is 0.050 cm T The Petri... 

For both humans and laboratory animals, one cannot currently distinguish between a radiation-induced cancer and a spontaneously occurring cancer (i.e., from an unknown cause). Therefore, statistical methods are used to determine whether radiation exposure is associated with an increase in cancer in a given study population. There have been several epidemiological studies in which definite dose-response relationships have been established for radiation-induced cancers. The best studied populations include atomic bomb survivors, Tinea capitis irradiation patients, ankylosing spondylitis irradiation patients, radium dial painters, radium therapy radium-224 patients, Thorotrast patients, uranium miners, Chernobyl fallout victims, and Mayak plutonium facility workers. 

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