Investigation of dose-rate effects and cell-cycle distribution under protracted exposure to ionizing radiation for various dose-rates

Small concentrations of certain additives can greatly modify the effects produced by radiation of macromolecules such as polymers and biological systems. Various mechanisms of protection can be envisaged, and these lead to different kinetics in protection effects. Most published work studies the elimination of the additive, rather than the change in the macromolecule. In previous papers in this series, the dose rate effects expected for radical reactions were observed for anthracene solutions in hexane and cyclohexane. With anthracene in dimethylsiloxane polymers, however, no such dependence was observed. This problem is studied in greater detail in the present paper. The additives studied were anthracene, iodine, sulphur and benzophenone, and their protective effect on the crosslinking of dimethylsiloxane polymer was investigated a t various dose rates. Contrary to generally accepted views on reaction mechanisms no dose-rate effect was observed; anthracene provided no protection against crosslinking, although it was itself destroyed. Iodine and colloidal sulphur provided a considerable measure of protection, but had no effect on gas evolution. Benzophenone also offered protection, but also reduced the gas yield. To explain these very different patterns of behaviour, it is necessary to modify some present views on the nature of the protection offered; this leads to a discussion as to the mechanism of crosslinking.

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Track Structure Considerations in Low Dose and Low Dose Rate Effects of Ionizing Radiation

Advances in Radiation Biology - Effects of Low Dose and Low Dose Rate Radiation ◽

10.1016/b978-0-12-035416-0.50006-9 ◽

1992 ◽

pp. 7-44 ◽

Cited By ~ 21

Author(s):

Dudley T. Goodhead

Keyword(s):

Ionizing Radiation ◽

Dose Rate ◽

Low Dose ◽

Track Structure ◽

Low Dose Rate ◽

Dose Rate Effects ◽

Rate Effects

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Dose rate effects of low-LET ionizing radiation on fish cells

Radiation and Environmental Biophysics ◽

10.1007/s00411-017-0706-5 ◽

2017 ◽

Vol 56 (4) ◽

pp. 433-441 ◽

Cited By ~ 7

Author(s):

Nguyen T. K. Vo ◽

Colin B. Seymour ◽

Carmel E. Mothersill

Keyword(s):

Ionizing Radiation ◽

Dose Rate ◽

Dose Rate Effects ◽

Rate Effects ◽

Fish Cells

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On the Amorphization of Silicon by Light Ion Implantation: Ion Flux and Substrate Temperature Effects

MRS Proceedings ◽

10.1557/proc-201-369 ◽

1990 ◽

Vol 201 ◽

Cited By ~ 4

Author(s):

A. Claverie ◽

A. Roumili ◽

N. Gessinn ◽

J. Beauvillain

Keyword(s):

Electron Microscopy ◽

Ion Implantation ◽

Substrate Temperature ◽

Dose Rate ◽

Energy Calculation ◽

Apparent Contradiction ◽

Near Surface ◽

Dose Rates ◽

Dose Rate Effects ◽

Rate Effects

AbstractIn this work, we have observed by cross-sectional electron microscopy (XTEM) and high resolution electron microscopy (HREM) the kinetics of silicon amorphization during nitrogen and helium bombardments for various dose rates and substrate temperatures. It is shown that the progression of the cla interfaces can be accurately described by the “Critical Damage Energy Density” (CDED) model for both ions at 100°K. At this temperature however, dose rate effects are unimportant. When increasing the substrate temperature up to 300°K, the amorphization efficiency is lowered. At 300°K dose rate effects are important and we show that for higher dose rates, the efficiency of the amorphization process is improved. In this case, the amorphous layers created by helium implantation are situated in the near surface region in apparent contradiction with damage calculations. The present experimental study demonstrates the competition which exists between the generation rate of point defects and the anihilation rate of these defects. Therefore, it is shown that the position of the a-layers created by light ion implantation at room temperature can be predicted by using a three-dimensional damage energy calculation.

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Dose-Rate Effects of Protons and Light Ions for DNA Damage Induction, Survival and Transformation in Apparently Normal Primary Human Fibroblasts

Radiation Research ◽

10.1667/rade-21-00138.1 ◽

2021 ◽

Author(s):

Paula V. Bennett ◽

Alicia M. Johnson ◽

Sarah E. Ackerman ◽

Pankaj Chaudhary ◽

Deborah J. Keszenman ◽

...

Keyword(s):

Dna Damage ◽

Cell Survival ◽

Dose Rate ◽

Low Dose ◽

Human Fibroblasts ◽

Dose Rates ◽

In Vitro Transformation ◽

Dose Rate Effects ◽

Rate Effects

We report on effects of low-dose exposures of accelerated protons delivered at high-dose rate (HDR) or a simulated solar-particle event (SPE) like low-dose rate (LDR) on immediate DNA damage induction and processing, survival and in vitro transformation of low passage NFF28 apparently normal primary human fibroblasts. Cultures were exposed to 50, 100 and 1,000 MeV monoenergetic protons in the Bragg entrance/plateau region and cesium-137 γ rays at 20 Gy/h (HDR) or 1 Gy/h (LDR). DNA double-strand breaks (DSB) and clustered DNA damages (containing oxypurines and abasic sites) were measured using transverse alternating gel electrophoresis (TAFE) and immunocytochemical detection/scoring of colocalized γ-H2AX pS139/53BP1 foci, with their induction being linear energy transfer (LET) dependent and dose-rate sparing observed for the different damage classes. Relative biological effectiveness (RBE) values for cell survival after proton irradiation at both dose-rates ranged from 0.61–0.73. Transformation RBE values were dose-rate dependent, ranging from ∼1.8–3.1 and ∼0.6–1.0 at low doses (≤30 cGy) for HDR and LDR irradiations, respectively. However peak transformation frequencies were significantly higher (1.3–7.3-fold) for higher doses of 0.5–1 Gy delivered at SPE-like LDR. Cell survival and transformation frequencies measured after low-dose 500 MeV/n He-4, 290 MeV/n C-12 and 600 MeV/n Si-28 ion irradiations also showed an inverse dose-rate effect for transformation at SPE-like LDR. This work demonstrates the existence of inverse dose-rate effects for proton and light-ion-induced postirradiation cell survival and in vitro transformation for space mission-relevant doses and dose rates.

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