The effects of dose rate on hematopoietic stem cells: Preliminary results

Belletti, S; Gallini, R; Magno, L

doi:10.1016/0360-3016(79)91222-7

Cited by 8 publications

(3 citation statements)

References 12 publications

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“…The dose-rate effect observed for 50 MeV/n proton radiation in these experiments results in the opposite effect of that observed for the 70 MeV/n experiments, since the high-dose-rate 50 MeV/n proton exposures resulted in a decreased RBE value and therefore a decreased effectiveness in reducing WBC counts compared to low-dose-rate 50 MeV/n proton exposures. Thus the dose-rate effect observed for 50 MeV/n proton in this study is most likely due to the inhomogeneous dose delivered during the 50 MeV/n proton exposures rather than being a result of radiation damage or radiation-induced adaptive responses, which are the current hypotheses for the dose-rate effect leading to sparing effects, which has been observed by other investigators (13–16). …”

Section: Discussionsupporting

confidence: 64%

Analysis of White Blood Cell Counts in Mice after Gamma- or Proton-Radiation Exposure

et al. 2011

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In the coming decades human space exploration is expected to move beyond low-Earth orbit. This transition involves increasing mission time and therefore an increased risk of radiation exposure from solar particle event (SPE) radiation. Acute radiation effects after exposure to SPE radiation are of prime importance due to potential mission-threatening consequences. The major objective of this study was to characterize the dose–response relationship for proton and γ radiation delivered at doses up to 2 Gy at high (0.5 Gy/min) and low (0.5 Gy/h) dose rates using white blood cell (WBC) counts as a biological end point. The results demonstrate a dose-dependent decrease in WBC counts in mice exposed to high- and low-dose-rate proton and γ radiation, suggesting that astronauts exposed to SPE-like radiation may experience a significant decrease in circulating leukocytes.

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Section: Discussionsupporting

confidence: 64%

Analysis of White Blood Cell Counts in Mice after Gamma- or Proton-Radiation Exposure

et al. 2011

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“…In dogs, toxicity to both gut [34] and lymphoid system [44] increased significantly when the TBI dose rate was increased by one log. Interestingly, other studies, using transfer of marrow cells from irradiated donors into irradiated recipients, found no significant differences in radiation sensitivity of CFU-S at different dose rates [5][6][7]9,45]. In one of those studies, using day 9 CFU-S as an end point, the investigators irradiated donor mice with TBI doses ranging from 100 to 500 cGy at dose rates of 8, 45, and 103 cGy/min [9].…”

Section: Discussionmentioning

confidence: 99%

“…Some investigators have concluded that increasing the dose rate increases the death rate of hematopoietic cells at a given total dose of TBI [1][2][3], although for smaller total doses (e.g., 200 cGy), it has been assumed that there is little dose-rate effect because most cell killing would be effected by single-hit mechanisms [4]. Other investigators maintain that there are no significant differences in radiation sensitivity of hematopoietic cells at different dose rates [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Dose rate-dependent marrow toxicity of TBI in dogs and marrow sparing effect at high dose rate by dose fractionation

Storb

Graham

et al. 1999

Biology of Blood and Marrow Transplantation

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We evaluated the marrow toxicity of 200 and 300 cGy total-body irradiation (TBI) delivered at 10 and 60 cGy/min, respectively, in dogs not rescued by marrow transplant. Additionally, we compared toxicities after 300 cGy fractionated TBI (100 cGy fractions) to that after single-dose TBI at 10 and 60 cGy/min. Marrow toxicities were assessed on the basis of peripheral blood cell count changes and mortality from radiation-induced pancytopenia. TBI doses studied were just below the dose at which all dogs die despite optimal support. Specifically, 18 dogs were given single doses of 200 cGy TBI, delivered at either 10 (n=13) or 60 (n=5) cGy/min. Thirty-one dogs received 300 cGy TBI at 10 cGy/min, delivered as either single doses (n=21) or three fractions of 100 cGy each (n=10). Seventeen dogs were given 300 cGy TBI at 60 cGy/min, administered either as single doses (n=5) or three fractions of 100 cGy each (n=10). Within the limitations of the experimental design, three conclusions were drawn: 1) with 200 and 300 cGy single-dose TBI, an increase of dose rate from 10 to 60 cGy/min, respectively, caused significant increases in marrow toxicity; 2) at 60 cGy/min, dose fractionation resulted in a significant decrease in marrow toxicities, whereas such a protective effect was not seen at 10 cGy/min; and 3) with fractionated TBI, no significant differences in marrow toxicity were seen between dogs irradiated at 60 and 10 cGy/min. The reduced effectiveness of TBI when a dose of 300 cGy was divided into three fractions of 100 cGy or when dose rate was reduced from 60 cGy/min to 10 cGy/min was consistent with models of radiation toxicity that allow for repair of sublethal injury in DNA.

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Bone Marrow

Nothdurft

1991

Medical Radiology

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The effects of dose rate on hematopoietic stem cells: Preliminary results

Cited by 8 publications

References 12 publications

Analysis of White Blood Cell Counts in Mice after Gamma- or Proton-Radiation Exposure

Analysis of White Blood Cell Counts in Mice after Gamma- or Proton-Radiation Exposure

Dose rate-dependent marrow toxicity of TBI in dogs and marrow sparing effect at high dose rate by dose fractionation

Bone Marrow

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