IS A DOSE DOSE-RATE EFFECTIVENESS FACTOR (DDREF) NEEDED FOLLOWING EXPOSURE TO LOW TOTAL RADIATION DOSES DELIVERED AT LOW DOSE-RATES?

2011 ◽  
Vol 100 (3) ◽  
pp. 262 ◽  
Author(s):  
Antone L. Brooks
Keyword(s):  
Dose Rate ◽  
Low Dose ◽  
Effectiveness Factor ◽  
Radiation Doses ◽  
Total Radiation ◽  
Dose Rates

scholarly journals Serum Metabolomic Alterations Associated with Cesium-137 Internal Emitter Delivered in Various Dose Rates

Metabolites ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 270
Author(s):  
Heng-Hong Li ◽  
Yun-Tien Lin ◽  
Evagelia C. Laiakis ◽  
Maryam Goudarzi ◽  
Waylon Weber ◽  
...  
Keyword(s):  
Dose Rate ◽  
Cumulative Dose ◽  
Low Dose ◽  
Biological Effects ◽  
Serum Samples ◽  
Dose Rates ◽  
Sphingosine 1 Phosphate ◽  
Cesium 137 ◽  
Dose Rate Effect ◽  
Medium Dose

Our laboratory and others have use radiation metabolomics to assess responses in order to develop biomarkers reflecting exposure and level of injury. To expand the types of exposure and compare to previously published results, metabolomic analysis has been carried out using serum samples from mice exposed to 137Cs internal emitters. Animals were injected intraperitoneally with 137CsCl solutions of varying radioactivity, and the absorbed doses were calculated. To determine the dose rate effect, serum samples were collected at 2, 3, 5, 7, and 14 days after injection. Based on the time for each group receiving the cumulative dose of 4 Gy, the dose rate for each group was determined. The dose rates analyzed were 0.16 Gy/day (low), 0.69 Gy/day (medium), and 1.25 Gy/day (high). The results indicated that at a cumulative dose of 4 Gy, the low dose rate group had the least number of statistically significantly differential spectral features. Some identified metabolites showed common changes for different dose rates. For example, significantly altered levels of oleamide and sphingosine 1-phosphate were seen in all three groups. On the other hand, the intensity of three amino acids, Isoleucine, Phenylalanine and Arginine, significantly decreased only in the medium dose rate group. These findings have the potential to be used in assessing the exposure and the biological effects of internal emitters.

scholarly journals Low-Dose-Rate Irradiation for 1 Hour Induces Protection Against Lethal Radiation Doses but Does Not Affect Life Span of DBA/2 Mice

Dose-Response ◽  
2016 ◽  
Vol 14 (4) ◽  
pp. 155932581667390 ◽  
Author(s):  
Nina Frederike Jeppesen Edin ◽  
Čestmír Altaner ◽  
Veronika Altanerova ◽  
Peter Ebbesen ◽  
Erik O. Pettersen
Keyword(s):  
Life Span ◽  
Dose Rate ◽  
Low Dose ◽  
Radiation Doses ◽  
Low Dose Rate

Evidence for dose and dose rate effects in human and animal radiation studies

2018 ◽  
Vol 47 (3-4) ◽  
pp. 97-112 ◽  
Author(s):  
M.P. Little
Keyword(s):  
Dose Rate ◽  
Dose Response ◽  
Low Dose ◽  
Atomic Bomb ◽  
Dose Range ◽  
Quadratic Model ◽  
Linear Quadratic ◽  
Dose Rates ◽  
Atomic Bomb Survivors ◽  
Linear Quadratic Model

For stochastic effects such as cancer, linear-quadratic models of dose are often used to extrapolate from the experience of the Japanese atomic bomb survivors to estimate risks from low doses and low dose rates. The low dose extrapolation factor (LDEF), which consists of the ratio of the low dose slope (as derived via fitting a linear-quadratic model) to the slope of the straight line fitted to a specific dose range, is used to derive the degree of overestimation (if LDEF > 1) or underestimation (if LDEF < 1) of low dose risk by linear extrapolation from effects at higher doses. Likewise, a dose rate extrapolation factor (DREF) can be defined, consisting of the ratio of the low dose slopes at high and low dose rates. This paper reviews a variety of human and animal data for cancer and non-cancer endpoints to assess evidence for curvature in the dose response (i.e. LDEF) and modifications of the dose response by dose rate (i.e. DREF). The JANUS mouse data imply that LDEF is approximately 0.2–0.8 and DREF is approximately 1.2–2.3 for many tumours following gamma exposure, with corresponding figures of approximately 0.1–0.9 and 0.0–0.2 following neutron exposure. This paper also cursorily reviews human data which allow direct estimates of low dose and low dose rate risk.

BIOSYNTHESIS OF QUERCETIN IN BUCKWHEAT: PART III

1960 ◽  
Vol 38 (1) ◽  
pp. 559-567 ◽  
Author(s):  
J. E. Watkin ◽  
A. C. Neish
Keyword(s):  
Dose Rate ◽  
Low Dose ◽  
Optimal Dose ◽  
Phenyllactic Acid ◽  
Maximum Percentage ◽  
Dose Rates ◽  
Percentage Conversion

The effect on the conversion of carbon14 to quercetin by a buckwheat plant caused by variation in the dose rate of a carbon 14-labelled precursor in μmoles over a 100-fold range has been studied. The results expressed as dilution of carbon14 varied over a 200-fold range for the same precursor with most of the variation being found at low dose rates. When expressed as the percentage of administered carbon14 converted to quercetin the results for acetate, D-glucose, and L-phenyllactic acid were mostly constant over this range but L-phenylalanine had a maximum percentage conversion or an optimal dose rate. An explanation of the results in metabolic terms has been attempted.It is recommended that the "percentage of C14 converted" be used to express results in plant biosynthetic work.

Radiolysis of dilute aqueous thiourea solutions

1966 ◽  
Vol 292 (1428) ◽  
pp. 122-133 ◽  
Keyword(s):  
Aqueous Solution ◽  
Dose Rate ◽  
Direct Effect ◽  
Indirect Effect ◽  
Radiation Doses ◽  
Limited Extent ◽  
Γ Radiation ◽  
Low Concentration ◽  
Dose Rates ◽  
Rapid Destruction

Thiourea, when present at low concentration, can act as a radiation protector to macromolecules (biological or polymeric) in aqueous solution. Previous work has shown that much of this protection occurs against the indirect effect. Thiourea can also protect against the direct effect, though to a more limited extent. In this paper the reactions of dilute aqueous thiourea solutions have been followed at a range of γ radiation doses and dose rates, and in the absence and presence of oxygen. The rapid destruction of thiourea confirms that the effect is primarily indirect, and almost independent of concentration, and dose rate over the range 10 to 500 mg/1. The breakdown products of thiourea can react further. In the presence of oxygen the loss of thiourea is more rapid, and different products are formed.

Gas phase radiolysis of hydrogen chloride, hydrogen bromide, and nitrous oxide with intense electron pulses

1969 ◽  
Vol 47 (20) ◽  
pp. 3783-3791 ◽  
Author(s):  
C. Willis ◽  
A. W. Boyd ◽  
D. A. Armstrong
Keyword(s):  
Nitrous Oxide ◽  
Dose Rate ◽  
Hydrogen Chloride ◽  
Low Dose ◽  
Hydrogen Bromide ◽  
Negative Ion ◽  
Dose Rates ◽  
Electron Pulses ◽  
Intense Electron ◽  
Very High

Hydrogen chloride and hydrogen bromide have been irradiated with single electron pulses at a very high intensity (1027 eV g−1 s−1) with a Febetron 705. At room temperature the yields of hydrogen from hydrogen chloride and hydrogen bromide, for pressures between 700 and 1200 Torr, are G(H2) = 8.1 ± 0.2 and G(H2) = 9.9 ± 0.3, respectively. These are the same as the yields observed at low dose rates. Detailed lifetime calculations, however, show that the mechanism is significantly different at the higher dose rate. Scavenger experiments with chlorine in hydrogen chloride show that the negative ion intermediates form thermal hydrogen atoms.The value of G(N2) = 12.4 ± 0.2 from nitrous oxide at a dose rate of 1027 eV g−1 s−1 is confirmed and the use of nitrous oxide as a dosimeter for pulsed electron beams is discussed. The higher nitrogen yield at Febetron dose rates appears to be due to changes in the reactions of electrons.

scholarly journals The effect of dose-rate on the yield of translocations and dominant lethals following spermatogonial irradiation of mice

1964 ◽  
Vol 5 (3) ◽  
pp. 468-472 ◽  
Author(s):  
R. J. S. Phillips ◽  
A. G. Searle
Keyword(s):  
Dose Rate ◽  
Low Dose ◽  
Previous Experiment ◽  
Male Mice ◽  
Dose Rates ◽  
Neonatal Lethality ◽  
Full Explanation ◽  
X Irradiation ◽  
Dominant Lethals ◽  
Dose Rate Effect

1. F1 (CSH♀ × 101♂) male mice were given 1200 r. 60Co Υ-irradiation over welve weeks and mated twelve weeks after the end of irradiation. The incidences of foetal and neonatal lethality and of semi-sterility in their offspring were compared with those in controls.2. Embryonic survival to 15 days in the irradiated series was 98·2% that of controls, while the incidence of semi-sterility was 0·9% compared with nil in the controls. Neither of these differences is significant.3. Comparison of these results with the significant rates of induction of dominant lethals and translocations in a previous experiment, in which a dose of 1200 r. acute x-irradiation was given to males of the same hybrid stock, show the existence of a dose-rate effect. Its magnitude cannot at present be accurately estimated.4. The reasons for this effect are discussed. It is concluded that the main cause of the lowered translocation yield is that restitution of breaks will be favoured at low dose-rates, with less opportunity for the formation of interchanges. This could partly account for the lowered rate of induction of dominant lethals as well, but a full explanation is not yet possible.

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

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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