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Tumor cells can be hypoxic and therefore less sensitive to X-rays because most of their effects are mediated by the free radicals produced by ionizing oxygen. It has meanwhile been shown that the most sensitive cells are those that are undifferentiated , well nourished, dividing quickly and highly active metabolically .
The best known explanation of the oxygen effect is the oxygen fixation hypothesis developed by Alexander in 1962, [9] which posited that radiation-induced non-restorable or "fixed" nuclear DNA lesions are lethal to cells in the presence of diatomic oxygen. [10] [11] Recent hypotheses include one based on oxygen-enhanced damage from first ...
Radioresistance is the level of ionizing radiation that organisms are able to withstand.. Ionizing-radiation-resistant organisms (IRRO) were defined as organisms for which the dose of acute ionizing radiation (IR) required to achieve 90% reduction (D10) is greater than 1,000 gray (Gy) [1]
Tumor cells in a hypoxic environment may be as much as 2 to 3 times more resistant to radiation damage than those in a normal oxygen environment. [5] Much research has been devoted to overcoming this problem including the use of high pressure oxygen tanks, blood substitutes that carry increased oxygen, hypoxic cell radiosensitizers such as ...
When dried and frozen, Deinococcus radiodurans could survive 140,000 grays, or units of X-and gamma-ray radiation, which is 28,000 times greater than the amount of radiation that could kill a person.
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However, for simplicity, the radiation weighting factors are not dependent on the type of tissue, and the values are conservatively chosen to be greater than the bulk of experimental values observed for the most sensitive cell types, with respect to external (external to the cell) sources. Radiation weighting factors have not been developed for ...
“The belief that exogenous electromagnetic field radiation is not harmful to biologic cells, systems, or organisms is to ignore over a hundred years of science that has understood the direct ...