Radioresistance
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Radioresistance is the property of organisms which are capable of living in environments with very high levels of ionizing radiation.
Radioresistance is surprisingly high in many organisms, in contrast to previously held views. For example, the study of environment, animals and plants around the Chernobyl accident area has revealed an unexpected survival of many species, despite the high radiation levels. A Brazilian study in a hill in the state of Minas Gerais which has high natural radiation levels from uranium deposits, has also shown many radioresistant insects, worms and plants.
Radiation can also help some plants to become more adapted to their environment by increasing the growth rate of the seeds. This helps them germinate faster.
Induced radioresistance
Radioresistance may be induced by exposure to small doses of ionizing radiation. Several studies have documented this effect in yeast, bacteria, protozoa, algae, plants, insects, as well as in in vitro mammalian and human cells and in animal models. Several cellular radioprotection mechanisms may be involved, such as alterations in the levels of some cytoplasmatic and nuclear proteins and increased gene expression, DNA repair and other processes.Inheritance of radioresistance
There is strong evidence that radioresistance can be genetically determined and inherited, at least in some organisms. Heinrich Nöthel, a geneticist from the Freie Universität Berlin carried out the most extensive study about radioresistance mutations using the common fruit fly, Drosophila melanogaster, in a series of 14 publications.Radioresistance in radiation oncology
Radioresistance is also a term sometimes used in medicine (oncology) for cancer cells which are difficult to treat with radiotherapy. Radioresistance of cancer cells may be intrinsic or induced by the radiation therapy itself.See also
- Radiosensitivity
- Deinococcus radiodurans (the most radioresistant organism, an extremophilic bacterium)
Radioresistance comparison
The comparison below is meant to give an indication of radioresistance for different species. There are generally big differences in radioresistance between experiments due to small number of specimens and being unable to control the testing environment (the number for human for instance was determined from the Hiroshima and Nagasaki bombings in WWII).| Organism | Lethal dose | LD50 | LD100 | Class/kingdom |
|---|---|---|---|---|
| Human | Mammals | |||
| Rat | 7.5 | Mammals | ||
| Mouse | 4.5-12 | 8.6-9 | Mammals | |
| Escherichia coli | 60 | 60 | Bacteria | |
| German cockroach | 64 | Insects | ||
| Fruit fly | 640 | Insects | ||
| Parasitoid wasp | 1800 | Insects | ||
| Deinococcus radiodurans | 15000 | Bacteria |
References
- Joiner, M.C. Induced Radioresistance: An Overview and Historical Perspective. Int J Rad Biol, 65(1): 79-84, 1994 ([Abstract])
- Ling CC, Endlich B. Radioresistance induced by oncogenic transformation. Radiat Res. 1989 Nov;120(2):267-79. PMID 2694214
- Cordeiro AR, Marques EK, Veiga-Neto AJ. Radioresistance of a natural population of Drosophila willistoni living in a radioactive environment. Mutat Res. 1973 Sep;19(3):325-9. PMID 4796403
- Nöthel H. Adaptation of Drosophila melanogaster populations to high mutation pressure: evolutionary adjustment of mutation rates. Proc Natl Acad Sci U S A. 1987 Feb;84(4):1045-9. PMID 3103121
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