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Will Radiation-Induced Bystander Effects Or Adaptive Responses Impact On The Shape Of The Dose Response Relationships At Low Doses Of Ionizing Radiation?, William F Morgan
Will Radiation-Induced Bystander Effects Or Adaptive Responses Impact On The Shape Of The Dose Response Relationships At Low Doses Of Ionizing Radiation?, William F Morgan
Dose-Response: An International Journal
Radiation induced bystander effects and adaptive responses are two phenomena that modulate cellular responses to low doses of ionizing radiation. Bystander effects generally exaggerate the effects of low doses of radiation by eliciting detrimental effects in nonirradiated cells, thus making the target for radiation effects greater than the volume irradiated. Adaptive responses on the other hand indicate that low doses of radiation can reduce damage induced by a second challenging dose. The potential impact of these two low dose effects on the shape of the dose response relationship will be discussed.
Adaptive And Bystander Responses In Human And Rodent Cell Cultures Exposed To Low Level Ionizing Radiation: The Impact Of Linear Energy Transfer, Sonia M De Toledo, Edouard I Azzam
Adaptive And Bystander Responses In Human And Rodent Cell Cultures Exposed To Low Level Ionizing Radiation: The Impact Of Linear Energy Transfer, Sonia M De Toledo, Edouard I Azzam
Dose-Response: An International Journal
To understand the potential impact on risk from exposure to low-level ionizing radiation, we have investigated the modulation of gene expression, induction of DNA damage and of neoplastic transformation in human or rodent cells derived from cultures exposed in vitro to low dose γ-rays (a low linear energy transfer radiation) or very low fluences of α-particles (a high linear energy transfer radiation). Pre-exposure of cells to a low γ-ray dose protected cells from the DNA damaging and killing effects induced by a subsequent acute challenge exposure to γ-rays. Furthermore, a low dose chronic exposure to γ-rays decreased the frequency of …
Development Of An In Vivo Assay For Detection Of Nontargeted Radiation Effects, Colin Seymour, Carmel Mothersill
Development Of An In Vivo Assay For Detection Of Nontargeted Radiation Effects, Colin Seymour, Carmel Mothersill
Dose-Response: An International Journal
An adaptive response may be defined as the effect of a small priming dose of radiation modifying the anticipated cellular response of the same tissues so as to alter the predicted response to a larger dose of radiation. We and others have demonstrated that at low radiation doses (less than 0.5 Gy) the lethal and mutational effect of the radiation is mainly, possibly entirely, due to the non-targeted effects. This is the dose range for priming doses in adaptive response protocols. In an associated presentation from our group, we demonstrate that the adaptive response may be explicable as a non …
Radiation-Induced Bystander And Adaptive Responses In Cell And Tissue Models, Kevin M Prise, Melvyn Folkard, Barry D Michael
Radiation-Induced Bystander And Adaptive Responses In Cell And Tissue Models, Kevin M Prise, Melvyn Folkard, Barry D Michael
Dose-Response: An International Journal
The use of microbeam approaches has been a major advance in probing the relevance of bystander and adaptive responses in cell and tissue models. Our own studies at the Gray Cancer Institute have used both a charged particle microbeam, producing protons and helium ions and a soft X-ray microprobe, delivering focused carbon-K, aluminium-K and titanium-K soft X-rays. Using these techniques we have been able to build up a comprehensive picture of the underlying differences between bystander responses and direct effects in cell and tissue-like models. What is now clear is that bystander dose-response relationships, the underlying mechanisms of action and …
Radiation-Induced Bystander Effects: Evidence For An Adaptive Response To Low Dose Exposures?, Carmel Mothersill, Colin Seymour
Radiation-Induced Bystander Effects: Evidence For An Adaptive Response To Low Dose Exposures?, Carmel Mothersill, Colin Seymour
Dose-Response: An International Journal
This paper reviews our current knowledge of the mechanisms underlying the induction of bystander effects by low dose, low-LET ionizing radiation and discusses how they may be related to observed adaptive responses or other protective effects of low dose exposures. Bystander effects appear to be the result of a generalized stress response in tissues or cells. The signals may be produced by all exposed cells, but the response appears to require a quorum in order to be expressed. The major response involving low LET radiation exposure discussed in the existing literature is a death response. This has many characteristics of …
Enhancement Of Bio-Protective Functions By Low Dose/Doserate Radiation, Kazuo Sakai, Takaharu Nomura, Yasihiro Ina
Enhancement Of Bio-Protective Functions By Low Dose/Doserate Radiation, Kazuo Sakai, Takaharu Nomura, Yasihiro Ina
Dose-Response: An International Journal
Effects of low-dose-rate gamma-irradiation on the process of tumorigenesis were investigated in mice treated with a carcinogenic agent or irradiated with high dose X-rays at a high dose rate. A prolonged gamma irradiation at approximately 1 mGy/hr suppressed the appearance of skin tumors induced by methylcholanthrene and delayed the appearance of radiation-induced thymic lymphomas in C57BL/6 mice. We also investigated the effects of low-dose-rate irradiation on disease model mice. In Type II diabetic C57BL/KsJdb/ db (db) mice, the urine glucose level was improved in some of the mice irradiated at 0.70 mGy/hr, but not in non-irradiated control mice. In MRL-lpr/lpr …
The Adaptive Response And Protection Against Heritable Mutations And Fetal Malformation, Dr Boreham, J-A Dolling, C Somers, J Quinn, Rej Mitchel
The Adaptive Response And Protection Against Heritable Mutations And Fetal Malformation, Dr Boreham, J-A Dolling, C Somers, J Quinn, Rej Mitchel
Dose-Response: An International Journal
There are a number of studies that show radiation can cause heritable mutations in the offspring of irradiated organisms. These “germ-line mutations” have been shown to occur in unique sequences of DNA called “minisatellite loci”. The high frequencies of spontaneous and induced mutations at minisatellite loci allow mutation induction to be measured at low doses of exposure in a small population, making minisatellite mutation a powerful tool to investigate radiation-induced heritable mutations. However, the biological significance of these mutations is uncertain, and their relationship to health risk or population fitness is unknown. We have adopted this mutation assay to study …
Radiation, Ecology And The Invalid Lnt Model: The Evolutionary Imperative, Peter A Parson
Radiation, Ecology And The Invalid Lnt Model: The Evolutionary Imperative, Peter A Parson
Dose-Response: An International Journal
Metabolic and energetic efficiency, and hence fitness of organisms to survive, should be maximal in their habitats. This tenet of evolutionary biology invalidates the linear-nothreshold (LNT) model for the risk consequences of environmental agents. Hormesis in response to selection for maximum metabolic and energetic efficiency, or minimum metabolic imbalance, to adapt to a stressed world dominated by oxidative stress should therefore be universal. Radiation hormetic zones extending substantially beyond common background levels, can be explained by metabolic interactions among multiple abiotic stresses. Demographic and experimental data are mainly in accord with this expectation. Therefore, non-linearity becomes the primary model for …