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In the News Archive

September 2015

THREE Web Site Address – One More Change

The THREE web site address has been changed once more, this time to the https or "HTTP Secure" protocol, which makes the newest THREE address to be: "https://three.jsc.nasa.gov". The main motivation for using HTTPS is authentication of the visited website and to protect the privacy and integrity of the exchanged data.1

All requests to the old addresses are automatically re-directed to the new address. It would be a good idea to update your THREE bookmark, but you can still access THREE with the older addresses if you don't.

1See Wikepedia entry "HTTPS"

POTENTIAL FOR CENTRAL NERVOUS SYSTEM EFFECTS FROM RADIATION EXPOSURE DURING SPACE ACTIVITIES, Phase I: OVERVIEW

This is a draft commentary from the National Council on Radiation Protection and Measurements (NCRP SC 1-24). This document has been posted for public review until September 25, 2015.

August 2015

THREE Web Site Address Change

The THREE web site has recently been relocated from its long-time home at USRA Houston to the Johnson Space Center. Although the actual URL (online address) has been changed from THREE.usra.edu to the new address of THREE.jsc.nasa.gov, the relocation will actually be transparent to users. All references to the old address will be automatically directed to the new address. It would be a good idea to update your bookmarks, but you will see no disruption in accessing THREE files if you don't.

The 20th Annual Workshop on Radiation Monitoring for the ISS

The 20th Annual Workshop on Radiation Monitoring for the International Space Station (WRMISS) will be held this year in Cologne, Germany  from September 8-10, 2015. Information on the workshop is available at http://www.wrmiss2015.de.  Files of previous years' presentations in pdf format are available at the permanent webpage of the workshop (www.wrmiss.org).

 (28)Silicon irradiation impairs contextual fear memory in B6D2F1 mice.

Raber J, Marzulla T, Stewart B, Kronenberg A, Turker MS.  Radiat Res. 2015 Jun; 183(6):708-12. Epub 2015 May 26.
Summary:
In mouse studies, C57Bl6/J homozygous wild-type mice and genetic mutant mice on a C57Bl6/J background have typically been used for assessing effects of space radiation on cognition and little is known about the radiation response of mice on a heterozygous background. In the study published in the June issue of Radiation Research, 28Si irradiation was shown to impair hippocampus-dependent contextual fear memory in C57Bl6/J x DBA2/J F1 (B6D2F1) mice three months following irradiation. In contrast, in an earlier study contextual fear memory was enhanced three months following irradiation of C57Bl6/J mice with 28Si. Thus, B6D2F1 mice seem more susceptible than C57Bl6/J mice to detrimental effects of 28Si irradiation and underline the importance of considering strains with distinct genetic backgrounds for evaluating the effects of space irradiation on the brain.

Dermatopathology effects of simulated SPE radiation exposure in the porcine model.

Sanzari JK, Diffenderfer ES, Hagan S, Billings PC, Gridley DS, Seykora JT, Kennedy AR, Cengel KA. Dermatopathology the porcine model. Life Sci Space Res. 2015 Jun 18.
Summary:
Solar particle event radiation increases an astronaut's risk of the acute radiation syndrome, prodromal effects, and/or skin damage. In this article, solar particle event-like radiation was simulated with either electron or proton radiation. Minipig skin was microscopically evaluated after nonhomogenous, total body radiation exposure at skin doses as high as 10 Gy. Maximum melanin deposition occurred at 14 days post-radiation with increased proliferation and skin thickening as well as DNA damage as late as 7 days post-radiation, indicative of post-inflammatory hyperpigmentation. These acute changes may be part of or trigger a larger inflammatory response, which may pose a hazard during deep space travel, especially if exacerbated by additional space environment factors.

Concepts and challenges in cancer risk prediction for the space radiation environment.

Barcellos-Hoff MH, Blakely EA, Burma S, Fornace AJ Jr, Gerson S, Hlatky L, Kirsch DG, Lederer U, Shay J, Wang Y, Weil MM. Life Sci Space Res. 2015. Epub 2015 Jul 17.
Summary:
This white paper from scientists who receive funding from the NASA Space Radiation Program addresses the current state of the cancer biology and issues related to animal models used to study the effects of space radiation on carcinogenesis.   Given that inherent uncertainties limit accurate cancer risk quantification for astronauts for deep space exploration, it is important to understand the biological mechanisms that increase cancer after radiation exposure and determine whether they impact risk modeling.  New experimental data suggest that radiation quality may increase the incidence of cancers with poor prognosis (e.g. metastatic); if so, determining the underlying biology may also provide routes to effective countermeasures.

Acute effects of exposure to Fe and O particles on learning and memory.

Rabin BM, Poulose SM, Carrihill-Knoll KL, Ramirez F, Bielinski DF, Heroux N, Shukitt-Hale B. Radiat Res. 2015 Jul 24. [Epub ahead of print]
Summary:
The experiments reported in this paper were designed to determine (1) the acute effects (24–48 hr) of exposure to 16O and 56Fe on cognitive performance; (2) whether exposure to HZE particles affected learning or memory; and (3) the relationship between HZE particle-induced oxidative stress and neuroinflammation in specific brain regions and cognitive performance. The results indicated that the acute effects of irradiation on cognitive performance are on memory, not learning. The effects of exposure to HZE particles on oxidative stress and neuroinflammation and their relationship to cognitive performance indicated that, although the effects of exposure are widespread, only changes in specific regions of the brain may be related to changes in cognitive function.

A single low dose of proton radiation induces long-term behavioral and electrophysiological changes in mice.

Bellone JA, Rudobeck E, Hartman RE, Szücs A, Vlkolinský R. Radiat Res. 2015 Jul 24. [Epub ahead of print]
Summary:
Exposure to high-LET charged particles, at doses similar to those anticipated during deep space missions, was previously shown in transgenic (TG) mice to promote Alzheimer's disease (AD)-like neurodegeneration. The authors found that proton radiation impaired reversal learning in the water maze and increased synaptic excitability in CA1 neurons, but suppressed their propensity for epileptiform activity. These baseline radiation responses to protons in healthy subjects suggest that astronauts traveling outside Earth's magnetosphere may be at increased risk of developing long-term decrements associated with hippocampal dysfunction.

 

A semiconductor radiation imaging pixel detector for space radiation dosimetry.

Kroupa M, Bahadori A, Campbell-Ricketts T, Empl A, Hoang SM, Idarraga-Munoz J, Rios R, Semones E, Stoffle N, Tlustos L, Turecek D, Pinsky L. . Life Sci Space Res. 2015 Jul 3. 
Summary:
A new generation of compact low-power active dosimeters is introduced. These new devices use state-of-the-art semiconductor technology to provide precise particle-by-particle measurements for environment evaluation. This article presents the core ideas of using this technology for space radiation monitoring along with a glimpse of developments to come.

 

Fractionated radiation exposure of rat spinal cords leads to latent neuro-inflammation in brain, cognitive deficits, and alterations in apurinic endonuclease.

Suresh Kumar MA, Peluso M, Chaudhary P, Dhawan J, Beheshti A, Manickam K, Thapar U, Pena L, Natarajan M, Hlatky L, Demple B, Naidu M. 1. PLoS One. 2015 Jul 24;10(7):e0133016.
Summary:
Spinal cords of rat were used as an in vivo model for measuring possible latent effects of protons and particle radiation on the differentiation oligodendrocyte precursor cells (OPC), using low LET (X-rays and protons (1 Gy)) and high LET (28Si/ 56Fe) radiation. This study focused on the role of the base excision repair protein Apurinic Endonuclease-1 (APE1) in the rat spinal cords OPC differentiation. Our studies show for the first time, that fractionation of protons cause latent damage to spinal cord architecture while fractionation of HZE (28Si) induced increases in APE1 with single dose, which then decreased with fractionation.

 

Irradiation of neurons with high-energy charged particles: An in silico modeling approach. 

Alp M, Parihar VK, Limoli CL, Cucinotta FA. PLoS Comput Biol. 2015 Aug; 11(8): e1004428.
Summary:  
This paper describes the spatial dependence of a particle's microscopic dose deposition events on a detailed neuron structure. Heavy ions including iron, carbon and hydrogen particles, and energetic electrons are considered. Results show that the heterogeneity of heavy particle tracks at low doses, compared to the more uniform dose distribution of electrons, juxtaposed with neuron morphology make it necessary to model the spatial dose painting for specific neuronal components.

 

Combined exposure to protons and 56Fe leads to overexpression of Il13 and reactivation of repetitive elements in the mouse lung.

Nzabarushimana E, Prior S, Miousse IR, Pathak R, Allen AR, Latendresse J, Olsen RHJ, Raber J, Hauer-Jensen M, Nelson GA, Koturbash I..Life Sci Space Res. 2015 Aug 18. 
Summary:
While previous studies have been devoted primarily to the effects of a single source of space radiation, there is an imperative need to utilize exposures to two or more sources to better simulate the occupational exposure that will be encountered by astronauts. In this study, the authors aimed to investigate the pro-fibrotic and epigenetic effects of exposure to protons and/or 56Fe ions in the dose range relevant to a space mission in the mouse lung 1 month after irradiation. Combined exposure to protons and 56Fe did not lead to detectable histopathological changes and increased expression of Tgfβ1 in the mouse lung. At the same time, combined exposure to protons and 56Fe resulted in substantially increased levels of Il13, a gene whose overexpression alone is sufficient to induce non-allergic asthma or induction of fibrosis, independently of Tgfβ1. Furthermore, decreased expression of the major maintenance DNA methyltransferase Dnmt1 and reactivation of repetitive elements - retrotransposons LINE-1 and SINE B1, and major and minor satellites were detected in the lungs of mice exposed to protons and 56Fe. The results of this study indicate that combined exposure to protons and 56Fe ions in the dose range relevant to a space mission may exert more severe pulmonary effects than exposure to either of these sources alone. 

July 2015

THREE Web Site Address Change

The THREE web site has recently been relocated from its long-time home at USRA Houston to the Johnson Space Center. Although the actual URL (online address) has been changed from THREE.usra.edu to the new address of THREE.jsc.nasa.gov, the relocation will actually be transparent to users. All references to the old address will be automatically directed to the new address. It would be a good idea to update your bookmarks, but you will see no disruption in accessing THREE files if you don't.

The 20th Annual Workshop on Radiation Monitoring for the ISS

The 20th Annual Workshop on Radiation Monitoring for the International Space Station (WRMISS) will be held this year in Cologne, Germany  from September 8-10, 2015. Information on the workshop is available at http://www.wrmiss2015.de.  Files of previous years' presentations in pdf format are available at the permanent webpage of the workshop (www.wrmiss.org).

 (28)Silicon irradiation impairs contextual fear memory in B6D2F1 mice.

Raber J, Marzulla T, Stewart B, Kronenberg A, Turker MS.  Radiat Res. 2015 Jun; 183(6):708-12. Epub 2015 May 26.
Summary:
In mouse studies, C57Bl6/J homozygous wild-type mice and genetic mutant mice on a C57Bl6/J background have typically been used for assessing effects of space radiation on cognition and little is known about the radiation response of mice on a heterozygous background. In the study published in the June issue of Radiation Research, 28Si irradiation was shown to impair hippocampus-dependent contextual fear memory in C57Bl6/J x DBA2/J F1 (B6D2F1) mice three months following irradiation. In contrast, in an earlier study contextual fear memory was enhanced three months following irradiation of C57Bl6/J mice with 28Si. Thus, B6D2F1 mice seem more susceptible than C57Bl6/J mice to detrimental effects of 28Si irradiation and underline the importance of considering strains with distinct genetic backgrounds for evaluating the effects of space irradiation on the brain.

Dermatopathology effects of simulated SPE radiation exposure in the porcine model.

Sanzari JK, Diffenderfer ES, Hagan S, Billings PC, Gridley DS, Seykora JT, Kennedy AR, Cengel KA. Dermatopathology the porcine model. Life Sci Space Res. 2015 Jun 18.
Summary:
Solar particle event radiation increases an astronaut's risk of the acute radiation syndrome, prodromal effects, and/or skin damage. In this article, solar particle event-like radiation was simulated with either electron or proton radiation. Minipig skin was microscopically evaluated after nonhomogenous, total body radiation exposure at skin doses as high as 10 Gy. Maximum melanin deposition occurred at 14 days post-radiation with increased proliferation and skin thickening as well as DNA damage as late as 7 days post-radiation, indicative of post-inflammatory hyperpigmentation. These acute changes may be part of or trigger a larger inflammatory response, which may pose a hazard during deep space travel, especially if exacerbated by additional space environment factors.

Concepts and challenges in cancer risk prediction for the space radiation environment.

Barcellos-Hoff MH, Blakely EA, Burma S, Fornace AJ Jr, Gerson S, Hlatky L, Kirsch DG, Lederer U, Shay J, Wang Y, Weil MM. Life Sci Space Res. 2015. Epub 2015 Jul 17.
Summary:
This white paper from scientists who receive funding from the NASA Space Radiation Program addresses the current state of the cancer biology and issues related to animal models used to study the effects of space radiation on carcinogenesis.   Given that inherent uncertainties limit accurate cancer risk quantification for astronauts for deep space exploration, it is important to understand the biological mechanisms that increase cancer after radiation exposure and determine whether they impact risk modeling.  New experimental data suggest that radiation quality may increase the incidence of cancers with poor prognosis (e.g. metastatic); if so, determining the underlying biology may also provide routes to effective countermeasures.

Badhwar-O'Neill 2014 galactic cosmic ray flux model description.

O'Neill PM, Golge S, Slaba TC.  Houston, TX: NASA Johnson Space Center, 2015 Mar. 32 p. NASA/TP-2015-218569.
Summary:
The Badhwar-O'Neill (BON) Galactic Cosmic Ray (GCR) model is based on GCR measurements from particle detectors. The model has mainly been used by NASA to certify microelectronic systems and for the analysis of radiation health risks to astronauts in space missions. The BON14 model numerically solves the Fokker-Planck differential equation to account for particle transport in the heliosphere due to diffusion, convection, and adiabatic deceleration under the assumption of a spherically symmetric heliosphere. The model also incorporates an empirical time delay function to account for the lag of the solar activity to reach the boundary of the heliosphere. This technical paper describes the most recent improvements in parameter fits to the BON model (BON14). Using a comprehensive measurement database, it is shown that BON14 is significantly improved over the previous version, BON11.

Lack of reliability in the disruption of cognitive performance following exposure to protons.  

Rabin, B. M., Heroux, N. A., Shukitt-Hale, B., Carrihill-Knoll, K. L., Beck, Z., & Baxter, C. (2015)   Radiation and Environmental Biophysics, 54: 285-295.
Summary:
A series of three replications were run to determine the reliability with which exposure to protons produces a disruption of cognitive performance, using a novel object recognition task and operant responding on an ascending fixed-ratio task.  For the first two replications, rats were exposed to head-only exposures to 1000 MeV/n protons at the NASA Space Radiation Laboratory.  For the third replication, subjects were given head-only or whole-body exposures to both 1000 and 150 MeV/n protons.  The results were characterized by a lack of consistency in the effects of exposure to protons on the performance of these cognitive tasks, both within and between replications.

Elucidation of changes in exposed human bronchial epithelial cells to radiations of increasing LET. 

Ding LH, Park S, Xie Y, Girard L, Minna JD, Story MD.  Mutagenesis. 2015 May 22. [Epub ahead of print]
Summary:
In this study, we investigated the role of ionizing radiation with increasing LETs in transforming human bronchial epithelial cells that varied in their oncogenic potential because of their genetic background. HBEC3KT cell lines were immortalized by overexpressing CDK4 and hTERT while the syngeneic HBEC3KT-R53RAS contain an additional  p53 knockdown vector and overexpress mutant kRAS.  Baseline transformation frequency for HBEC3KT is 10 times lower than its progressed counterpart HBEC3KT-P53RAS. As early as 6 day post-IR, cellular transformation was 1-2 logs higher increased in the oncogenically progressed HBEC3KT-p53RAS cells while gene expression profiles identified pathways that contribute to transformation including HIF-1α, mTOR, IGF-1, RhoA and the ERK/MAPK pathways upregulated in the progressed cell line. Our data suggested greater risk of lung cancer for heavy particles exposure in individuals harboring cancer-prone genetic changes.

What happens to your brain on the way to Mars

Vipan K. Parihar, Barrett Allen, Katherine K. Tran, Trisha G. Macaraeg, Esther M. Chu, Stephanie F.Kwok, Nicole N. Chmielewski, Brianna M. Craver, Janet E. Baulch, Munjal M. Acharya, Francis A.Cucinotta, Charles L. Limoli. published Sci. Adv. 2015;1:e1400256 1 May 2015 .
Summary:
Our study provides evidence that suggests exposure to space radiation poses a risk for developing cognitive decrements.  Mice subjected to low doses of charged particles showed impaired learning and memory when subjected to behavioral testing 6 weeks later.  Cognitive deficits coincided with a range of structural and synaptic alterations to neurons located in the medial prefrontal cortex.  Reductions in dendritic complexity and spine density can directly disrupt neurotransmission and cognition.  Our findings suggest that similar types of cognitive complications may arise in astronauts subjected to the space radiation environment during a long term deep space mission to Mars.

Experimental microdosimetry: History, applications and recent technical advances.

Braby LA. Radiat Prot Dosimetry. 2015 Apr 15. [Epub ahead of print]
Summary:
This paper summarizes the 50 year development of microdosimetry detectors from delicate laboratory research instruments to rugged detectors that can be used in a wide variety of radiation environments. The relative biological risk presented by different types of ionizing radiation can be estimated based on the amount of energy each type deposits in small volumes such as a cell nucleus.  Radiations which deposit a large amount of energy in a few small volumes tend to be more damaging than radiations that deposit a small amount of energy in a large number of small volumes, even though the total amount of energy deposited in an organ is the same.  The characterization of energy deposition in small volumes, known as microdosimetry, has been the basis of a sequence of instruments used to evaluate radiation exposure on the STS and ISS for nearly two decades.

Issues for Simulation of Galactic Cosmic Ray Exposures for Radiobiological Research at Ground Based Accelerators

Kim Myung-Hee Y, Rusek Adam, Cucinotta Francis A. Frontiers in Oncology. 2015. Vol 5(00122).
Summary
We performed extensive simulation studies using the stochastic transport code, GERMcode (GCR Event Risk Model) to define a GCR reference field using 9 HZE particle beam–energy combinations each with a unique absorber thickness to provide fragmentation and 10 or more energies of proton and 4He beams. A kinetics model of HZE particle hit probabilities suggests that experimental simulations of several weeks will be needed to avoid high fluence rate artifacts, which places limitations on the experiments to be performed. Ultimately risk estimates are limited by theoretical understanding, and focus on improving knowledge of mechanisms and development of experimental models to improve this understanding should remain the highest priority for space radiobiology research.

June 2015

NASA Space Radiobiology Research Announcement

NASA Research Announcement (NRA) NNJ14ZSA001N-RADIATION, entitled "Ground-Based Studies in Space Radiobiology” was released on March 4, 2015. This NRA solicits ground-based proposals for the Space Radiation Program Element (SRPE) component of the Human Research Program (HRP). This response area is Appendix D of the Human Exploration Research Opportunities (HERO) NRA (NNJ14ZSA001N).

The NRA solicits research addressing critical questions in the major space radiation risk areas of radiation carcinogenesis, acute and late effects of space radiation on the central nervous system and risk of space radiation induced cardiovascular diseases. The solicitation also requests proposals under three special topic areas including validation studies for the Galactic Cosmic Radiation (GCR) Simulator project, biological countermeasure development for space radiation induced cancers, and development of multiscale models for risk prediction of radiation induced disease.

Proposals will utilize beams of high energy heavy ions simulating space radiation at the NASA Space Radiation Laboratory (NSRL), at Brookhaven National Laboratory (BNL) in Upton, New York.

The full text of the solicitation appendix is available on the NASA Research Opportunities homepage at http://tinyurl.com/2015-Radiation.

Invited Step-2 proposals are due June 22, 2015

What happens to your brain on the way to Mars

Vipan K. Parihar, Barrett Allen, Katherine K. Tran, Trisha G. Macaraeg, Esther M. Chu, Stephanie F.Kwok, Nicole N. Chmielewski, Brianna M. Craver, Janet E. Baulch, Munjal M. Acharya, Francis A.Cucinotta, Charles L. Limoli. published Sci. Adv. 2015;1:e1400256 1 May 2015 .
Summary:
Our study provides evidence that suggests exposure to space radiation poses a risk for developing cognitive decrements.  Mice subjected to low doses of charged particles showed impaired learning and memory when subjected to behavioral testing 6 weeks later.  Cognitive deficits coincided with a range of structural and synaptic alterations to neurons located in the medial prefrontal cortex.  Reductions in dendritic complexity and spine density can directly disrupt neurotransmission and cognition.  Our findings suggest that similar types of cognitive complications may arise in astronauts subjected to the space radiation environment during a long term deep space mission to Mars.

Experimental microdosimetry: History, applications and recent technical advances.

Braby LA. Radiat Prot Dosimetry. 2015 Apr 15. [Epub ahead of print]
Summary:
This paper summarizes the 50 year development of microdosimetry detectors from delicate laboratory research instruments to rugged detectors that can be used in a wide variety of radiation environments. The relative biological risk presented by different types of ionizing radiation can be estimated based on the amount of energy each type deposits in small volumes such as a cell nucleus.  Radiations which deposit a large amount of energy in a few small volumes tend to be more damaging than radiations that deposit a small amount of energy in a large number of small volumes, even though the total amount of energy deposited in an organ is the same.  The characterization of energy deposition in small volumes, known as microdosimetry, has been the basis of a sequence of instruments used to evaluate radiation exposure on the STS and ISS for nearly two decades.

Issues for Simulation of Galactic Cosmic Ray Exposures for Radiobiological Research at Ground Based Accelerators

Kim Myung-Hee Y, Rusek Adam, Cucinotta Francis A. Frontiers in Oncology. 2015. Vol 5(00122).
Summary
We performed extensive simulation studies using the stochastic transport code, GERMcode (GCR Event Risk Model) to define a GCR reference field using 9 HZE particle beam–energy combinations each with a unique absorber thickness to provide fragmentation and 10 or more energies of proton and 4He beams. A kinetics model of HZE particle hit probabilities suggests that experimental simulations of several weeks will be needed to avoid high fluence rate artifacts, which places limitations on the experiments to be performed. Ultimately risk estimates are limited by theoretical understanding, and focus on improving knowledge of mechanisms and development of experimental models to improve this understanding should remain the highest priority for space radiobiology research.

May 2015

NASA Space Radiobiology Research Announcement

NASA Research Announcement (NRA) NNJ14ZSA001N-RADIATION, entitled "Ground-Based Studies in Space Radiobiology” was released on March 4, 2015. This NRA solicits ground-based proposals for the Space Radiation Program Element (SRPE) component of the Human Research Program (HRP). This response area is Appendix D of the Human Exploration Research Opportunities (HERO) NRA (NNJ14ZSA001N).

The NRA solicits research addressing critical questions in the major space radiation risk areas of radiation carcinogenesis, acute and late effects of space radiation on the central nervous system and risk of space radiation induced cardiovascular diseases. The solicitation also requests proposals under three special topic areas including validation studies for the Galactic Cosmic Radiation (GCR) Simulator project, biological countermeasure development for space radiation induced cancers, and development of multiscale models for risk prediction of radiation induced disease.

Proposals will utilize beams of high energy heavy ions simulating space radiation at the NASA Space Radiation Laboratory (NSRL), at Brookhaven National Laboratory (BNL) in Upton, New York.

The full text of the solicitation appendix is available on the NASA Research Opportunities homepage at http://tinyurl.com/2015-Radiation.

Invited Step-2 proposals are due June 22, 2015

What happens to your brain on the way to Mars

Vipan K. Parihar, Barrett Allen, Katherine K. Tran, Trisha G. Macaraeg, Esther M. Chu, Stephanie F.Kwok, Nicole N. Chmielewski, Brianna M. Craver, Janet E. Baulch, Munjal M. Acharya, Francis A.Cucinotta, Charles L. Limoli. published Sci. Adv. 2015;1:e1400256 1 May 2015 .
Summary:
Our study provides evidence that suggests exposure to space radiation poses a risk for developing cognitive decrements.  Mice subjected to low doses of charged particles showed impaired learning and memory when subjected to behavioral testing 6 weeks later.  Cognitive deficits coincided with a range of structural and synaptic alterations to neurons located in the medial prefrontal cortex.  Reductions in dendritic complexity and spine density can directly disrupt neurotransmission and cognition.  Our findings suggest that similar types of cognitive complications may arise in astronauts subjected to the space radiation environment during a long term deep space mission to Mars.

Simulation of the radiolysis of water using Green's functions of the diffusion equation

Plante I, Cucinotta FA. Radiat Prot Dosimetry. 2015 Apr 20. [Epub ahead of print]
Summary:
Green's functions of the diffusion equation (GFDEs) for partially diffusion-controlled reactions represent the probability distribution for a pair of particles to be separated by the inter-particle distance r at time t, assuming that they were initially at separation distance r0. The integral is the survival probability of the pair. In this paper, the first simulation results obtained for the radiolysis of water by 300-MeV protons are presented, using radiation track structures calculated by the code RITRACKS as a starting point for the simulation.

The role of DNA cluster damage and chromosome aberrations in radiation-induced cell killing: A theoretical approach

Ballarini F, Altieri S, Bortolussi S, Carante M, Giroletti E, Protti N. Radiat Prot Dosimetry. 2015 Apr 15. [Epub ahead of print]
Summary:
This paper presents a biophysical model of radiation cell killing called BIANCA (BIophysical ANalysis of Cell death and chromosome Aberrations), which assumes that certain chromosome aberrations ("lethal aberrations") lead to cell death, and that chromosome aberrations are due to mm-scale rejoining of chromosome fragments deriving from DNA "cluster lesions" (CLs); the CL yield and the threshold distance governing chromosome-fragment rejoining are adjustable parameters. The agreement between simulated survival curves and experimental data on human and hamster cells exposed to photons, light ions and heavier ions suggests that lethal aberrations may play an important role in cell killing for different cell lines and different radiation types. Furthermore, the results are consistent with the hypothesis that the critical DNA lesions leading to cell death and other endpoints are DSB clusters at sub-micrometric scale (possibly involving DNA fragments with size at the kilo-bp scale), and that the effects of such critical lesions are modulated by mm-scale proximity effects during DNA-damage processing.

Binary-Encounter-Bethe direct effect of ionising radiation.

Plante I, Cucinotta FA Radiat Prot Dosimetry. 2015 Apr 13. [Epub ahead of print]
Summary:
This paper describes the Binary-Encounter-Bethe (BEB) model of cross sections for ionization of DNA bases, sugars and phosphates by electrons. In this model, the differential cross section is calculated for each electron using the electron binding energy, the mean kinetic energy and the occupancy number of each orbital as parameters.  Additionally, the paper reports two sampling algorithm. The first is used to determine the energy loss occurring during an ionization event in DNA using the BEB model. The second algorithm is used to determine the distance of an electron to the next interaction when it crosses media with different cross sections, which is the case when the trajectory of an electron intersects DNA.

Biophysics of NASA Radiation Quality Factors.

Francis A. Cucinotta. Radiat Prot Dosimetry (2015) 
doi: 10.1093/rpd/ncv144. First published online: April 16, 2015
Summary:
NASA has implemented new radiation quality factors (QFs) for projecting cancer risks from space radiation exposures to astronauts. The NASA QFs are based on particle track structure concepts with parameters derived from available radiobiology data, and NASA introduces distinct QFs for solid cancer and leukaemia risk estimates. A key feature of the NASA QFs is to represent the uncertainty in the QF assessments and evaluate the importance of the QF uncertainty to overall uncertainties in cancer risk projections. In this article, the biophysical basis for the probability distribution functions representing QF uncertainties is reviewed, and approaches needed to reduce uncertainties are discussed.

Safe days in space with acceptable uncertainty from space radiation exposure.

Francis A. Cucinotta, Murat Alp,  Blake Rowedder, Myung-Hee Y. Kim. Life Sciences in Space Research. Volume 5, April 2015, Pages 31–38 
Summary:
In this paper, we evaluate probability distribution functions and the number or “safe days” in space, which are defined as the mission length where risk limits are not exceeded, for several mission scenarios at different acceptable levels of uncertainty. In addition, we briefly discuss several important issues in risk assessment including non-cancer effects, the distinct tumor spectra and lethality found in animal experiments for HZE particles compared to background or low LET radiation associated tumors, and the possibility of non-targeted effects (NTE) modifying low dose responses and increasing relative biological effectiveness (RBE) factors for tumor induction.

Low-dose energetic protons induce adaptive and bystander effects that protect human cells against DNA damage caused by a subsequent exposure to energetic iron ions

Buonanno M, De Toledo SM, Howell RW, Azzam EI. J Radiat Res. 2015 Mar 23. 
Summary:   
Buonanno et al. measured DNA damage in normal human cells exposed to protons followed at a subsequent time by energetic HZE particles. The spread of signaling events from low dose proton-irradiated cells to non-irradiated cells in their vicinity (i.e. bystanders), and the ensuing response of the latter cells to a challenge by HZE particles, was also examined. The results suggest that these studies should be extended to evaluate cytogenetic effects and other endpoints following exposures to mixed fields of space radiation delivered chronically at low dose rates.

April 2015

Particle Radiation-Induced Non-targeted Effects in Bone-Marrow-Derived Endothelial Progenitor Cells

Goukassian DA, Sasi SP, Park D, Muralidharan S, Wage J, Kiladjian A, Onufrak J, Enderling H, Yan X. Stem Cell International, May 2015  [In press].
Summary:
Our studies show that exposure to single low-dose proton (90 cGy, 1 GeV) or iron (15 cGy, 1 GeV/n) radiation culminated in persistent IR-induced DNA damage in BM-EPCs over a period of one month; increased levels of cytokine and chemokine expression over 24 h along with a cyclical increase in apoptosis over 28 days post-IR. This may lead to BM-EPC dysfunction and eventually contribute to the increased risk for development of cardiovascular and neurodegenerative diseases. Therefore, identifying the role of specific cytokines responsible for IR-induced NTE in BM may allow development of mitigating factors to prevent long-term and cyclical loss of stem and progenitors cells in the BM milieu.

Persistent oxidative stress in human neural stem cells exposed to low fluences of charged particles

Baulch JE, Craver BM, Tran KK, Yu L, Chmielewski N, Allen BD, Limoli CL. Redox Biol. 2015 Aug 11;5:24-32. Epub 2015 Mar 11.
Summary: In this study we investigated whether space relevant fluences of charged particles caused oxidative stress in cultures of human neural stem cells that was proportional to the microdosimetric properties of the incident particle. Dose and temporal responses for radiation-induced oxidative stress were probed through the use of intracellular fluorogenic dyes that exhibit relative specificity for certain reactive species. Increased fluorescent signals derived from the oxidation of selected redox sensitive dyes provided a quantitative measure of oxidative stress after exposure. Data showed that the total dose, rather than particle energy and/or LET was the predominate factor dictating the extent and duration of oxidative stress in irradiated populations of human neural stem cells.

A New Approach to Reduce Uncertainties in Space Radiation Cancer Risk Predictions.

Cucinotta, F.S. 2015;PLOS ONE 10.1371/journal.pone.0120717
Summary:
The prediction of space radiation induced cancer risk carries large uncertainties with two of the largest uncertainties being radiation quality and dose-rate effects. In risk models the ratio of the quality factor (QF) to the dose and dose-rate reduction effectiveness factor (DDREF) parameter is used to scale organ doses for cosmic ray proton and high charge and energy (HZE) particles to a hazard rate for γ-rays derived from human epidemiology data.. Here I report on an analysis of a maximum QF parameter and its uncertainty using mouse tumor induction data. Because experimental data for risks at low doses of γ-rays are highly uncertain which impacts estimates of maximum values of relative biological effectiveness (RBEmax), I developed an alternate QF model, denoted QFγAcute where QFs are defined relative to higher acute γ-ray doses (0.5 to 3 Gy). The alternate model reduces the dependence of risk projections on the DDREF, however a DDREF is still needed for risk estimates for high-energy protons and other primary or secondary sparsely ionizing space radiation components.  In addition, I discuss how a possible qualitative difference leading to increased tumor lethality for HZE particles compared to low LET radiation and background tumors remains a large uncertainty in risk estimates.

Ionizing radiation stimulates expression of pro-osteoclastogenic genes in marrow and skeletal tissue

Alwood JS, Shahnazari M, Chicana B, Schreurs AS, Kumar A, Bartolini A, Shirazi-Fard Y, Globus RK. J Interferon Cytokine Res. 2015 Mar 3. [Epub ahead of print]
Summary:
Irradiation causes a very rapid loss of mineralized bone tissue via increased resorption by osteoclasts. In this study, adult mice were exposed to HZE (56Fe) or 137Cs radiation to evaluate expression levels of genes known to mediate osteoclastogenesis.  This work shows a time-dependent, radiation-induced increase in skeletal expression of Rankl, the obligate cytokine for osteoclast differentiation, as well as other pro-resorption cytokines (Mcp1, Tnf, Csf1, Il6), markers of osteoclast activation (Acp5, Ctk, NfatC1), and oxidative stress responses (nfe2l2).  These molecular responses to radiation preceded (< 3 days) the manifestation of bone loss (3–7 days). The findings have relevance to skeletal fragility caused by radiation exposure either on Earth or in space.

Space radiation risks to the central nervous system (Review)

Cucinotta, F.A., Alp, M., Sulzman, F.M., Wang, M. Life Sci. Space Res, 2014;2:54–69
Summary:
In this report we summarize recent space radiobiology studies of CNS effects from particle accelerators simulating space radiation using experimental models, and make a critical assessment of their relevance  with respect to doses and the dose rates to be incurred on a Mars Mission. Prospects for understanding dose, dose-rate and radiation quality dependencies of CNS effects and extrapolation to human risk assessments are described.

Measurements of the neutron spectrum in transit to Mars on the Mars Science Laboratory

Köhler J, Ehresmann B, Zeitlin C, Wimmer-Schweingruber RF,J, Böttcher S, Böhm E, Burmeister S, Guo J, Lohf H, Martin C, Posner A, Rafkin S. Life Sci Space Res. 2015 Mar 24. [Article in Press] Article citation (from SPACELINE):
Summary:
The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011. Although designed for measuring the radiation on the surface of Mars, the Radiation Assessment Detector (RAD) used this unique opportunity to measure the radiation environment inside the spacecraft during the 253-day cruise to Mars.RAD measures neutral particles with two scintillators enclosed by an anti-coincidence. One of the scintillators has a high-Z and therefore a high sensitivity for gamma-rays, the other scintillator has a high proton content and therefore a high sensitivity for neutrons. In this work an inversion method is applied to the RAD neutral particle measurements to obtain the neutron and gamma spectra as well as neutron dose and dose equivalent.

Evaluation of the new radiation belt AE9/AP9/SPM model for a cislunar mission

Badavi FF, Walker SA, Santos Koos LM. Acta Astronaut. 2014;102:156-68.
Summary:
A multi-vehicle mission is planned for the epoch of February 2020 from LEO to the Earth–moon Lagrange-point two (L2), located approximately 63,000km beyond the orbit of the Earth–Moon binary system. During the LEO–GEO transit, the crew and cargo vehicles will encounter exposure from trapped particles and attenuated GCR, followed by free space exposure due to GCR and SEP. In this work, the amount of exposure acquired within the trapped field, along the design trajectory of the crew vehicle, using the new AE9/AP9/SPM model is evaluated against the older AE8/AP8 model. The analysis is then extended to the GCR dominated en-route, cislunar L2 space and return trajectories in order to provide cumulative exposure estimates for the duration of the mission.

Validation of the new trapped environment AE9/AP9/SPM at low Earth orbit

Badavi FF. Adv Space Res. 2014;54(6):917-28.
Summary:
One goal of this paper is to validate the older AE8/AP8 and the new AE9/AP9/SPM trapped radiation models against ISS dosimetric measurements for a silicon based detector, and to assess the improvements in the AE9/AP9/SPM model as compared to AE8/AP8 using both isotropic and anisotropic spectra. For angular validation AP8 and AP9 are compared with  measurements from the compact environment anomaly sensor (CEASE).  science instrument package, flown June 2000–July 2006. Particular emphasis is put on the validation of proton flux profiles at differential 40 MeV and integral >40 MeV, in the vicinity of the South Atlantic Anomaly, where protons exhibit east–west (EW) anisotropy and have a relatively narrow pitch angle distribution.

March 2015

Data integration reveals key homeostatic mechanisms following low dose radiation exposure

Susan C. Tilton, Melissa M. Matzke, Marianne B. Sowa, David L. Stenoien, Thomas J. Weber, William F. Morgan, and Katrina M. Waters, Toxicol Appl Pharmacol. 2015 Feb 2. pii: S0041-008X(15)00042-3. doi: 10.1016/j.taap.2015.01.019. [Epub ahead of print].
Summary:
This study develops a systems approach to define pathways regulated by low dose radiation exposures and to understand how a complex biological system responds to subtle perturbations in its environment.  We have examined the temporal response of the dermal and epidermal layers of an irradiated 3D full thickness skin model using transcriptomic, proteomic, phosphoproteomic and metabolomic strategies to generate a significant amount of heterogeneous data.  The integration of these varied data sets using both top down and bottom up approaches identified novel signaling pathways that would not be clearly observed by any single ‘omic technology and suggests persistent alterations in cellular and tissue homeostatic regulation occur following low dose radiation exposures in skin.  The goal of these systems approaches is to enable a transition from qualitative observations to a quantitative and ultimately predictive science.

Overview of the Liulin type instruments for space radiation measurement and their scientific results

T.P. Dachev, J.V. Semkova, B.T. Tomov, Yu.N. Matviichuk, P.G. Dimitrov, R.T. Koleva, St.Malchev, N.G. Bankov, V.A. Shurshakov, V.V. Benghin, E.N. Yarmanova, O.A. Ivanova, D.-P. Häder, M. Lebert, M.T. Schuster, G. Reitz, G. Horneck, Y. Uchihori, H. Kitamura, O. Ploc, J. Cubancak, I. Nikolaev, Life Sciences in Space Research, Volume 4, January 2015, Pages 92–114.
Summary:
The paper presents an overview of the different modifications of the Liulin type spectrometer-dosimeters, which were developed in the late 1980s and have been in use since then. Up to now Liulin type instruments were developed for 14 experiments in space: 1 on Mir space station, 6 on ISS, and other 7 on different satellites including Chandrayaan-1 satellite at 100 km orbit around the Moon. 2 of them were lost on Mars-96 and Phobos-Grunt missions. Currently there are 3 active Liulin type experiments on ISS. The data analysis procedure allows characterization of the different main space radiation sources as GCR, inner radiation belt protons and outer radiation belt electrons. There are two major discoveries in the ISS radiation environment: the first is the large outside doses from relativistic electrons in the outer radiation belt, while the second is the decrease in the ISS SAA dose rate during the US space shuttle dockings. Liulin spectrometers were also used by different scientific groups for monitoring of the radiation environment on thousands of aircraft flights and balloons. The main advantages of the Liulin type spectrometers are their low weight (100–500 g), low power consumption (100–500 mW) and low cost.

Relative Effectiveness at 1 Gy after Acute and Fractionated Exposures of Heavy Ions with Different Linear Energy Transfer for Lung Tumorigenesis

Ya Wang, Xiang Wang, Alton B. Farris III, Ping Wang, Xiangming Zhang, Hongyan Wang, and (2015),  Radiation Research: February 2015, Vol. 183, No. 2, pp. 233-239.
Summary:
Lung cancer is the most commonly diagnosed cancer as well as the leading cause of cancer death in humans; therefore, studying radiation-induced lung tumorigenesis is critical for estimating the risk of space radiation to astronauts. In this study, we show that all these tested HZE particles (iron, silicon, oxygen) induced a higher incidence of lung tumorigenesis than x-rays, the relative effectiveness at 1 Gy was > 6 and silicon exposure induced more aggressive lung tumors.

Novel images and novel locations of familiar images as sensitive translational cognitive tests in humans

J. Raber. published in Behav Brain Res. 2015 Feb 2. [Epub ahead of print].
Summary:
Cognitive tests involving preferential exploration of familiar objects in novel locations and of novel objects are particularly sensitive to detect effects of space irradiation in rodents. Based on the rodent test of object recognition, a human test of object recognition was developed, the Novel Image Novel Location (NINL) test, containing panels with three images each. As this test does not involve language and is sensitive to detect of apolipoprotein E4, a risk factor for age-related cognitive decline and Alzheimer's disease, in the healthy oldest-old (mean age 81 years), it would also be good to consider the NINL test for assessing cognitive performance in astronauts during and/or following space missions.

Nanoscale analysis of clustered DNA damage after high-LET irradiation by quantitative electron microscopy - The heavy burden to repair

Rübe CE, Lorat Y, Brunner CU, Schanz S, Jakob B, Taucher-Scholz G. DNA Repair (Amst). 2015 Jan 28. pii: S1568-7864(15)00019-1. doi: 10.1016/j.dnarep.2015.01.007.
Summary:
The spatial distribution of energy deposition on the scale of DNA, cells and tissue for both low- and high-LET radiation is important in determining the subsequent biological response in DNA, cells and ultimately people. In irradiated cells, the biological response has been shown to be critically dependent on the clustering of DNA damage on the nanometer scale, with high-LET radiation not only producing a higher frequency of complex DNA damage but also typically producing damage sites of greater complexity than those produced by low-LET radiation.

Here, using a new approach based on electron microscopic detection of immunogold-labeled repair factors we visualized different types of DNA lesions (SSBs, DSBs, clustered lesions) in the chromatin ultrastructure of human cells and characterized the spatio-temporal DNA damage pattern at the nanometer scale after low-LET and high-LET radiation. We show that high-LET radiation produced highly clustered DNA lesions within the particle trajectories, with multiple DSBs localized in regions of compact heterochromatin. Compared to sparsely ionizing radiation, high-LET radiation induced clearly higher yields of DSBs with up to ~500 DSBs per µm3 track volume. These clustered DNA lesions were repaired with slower kinetics and large fractions of these heterochromatic DSBs remained unrepaired. These unrepaired and/or misrepaired DNA lesions may contribute to the observed higher relative biological effectiveness for cell killing, chromosomal aberrations, mutagenesis, and carcinogenesis in high-LET radiated cells.

Previous In the News Items

A lifetime in biophysics

Blakely E., CERN COURIER. Aug 26, 2014
Summary: 
Eleanor Blakely talks about her work at Berkeley that began with pioneering research into the use of ion beams for hadron therapy.

Low- and High-LET Radiation Drives Clonal Expansion of Lung Progenitor Cells In Vivo

Farin, A. M., Manzo, N. D., Terry, K. L., Kirsch, D. G. and Stripp, B. R. Radiat. Res. 183,124–132 (2015).
Summary: 
Astronauts are exposed to varying doses and qualities of ionizing radiation during space travel. However, little is known about the effects of ionizing radiation on epithelial progenitor cells that maintain the respiratory system. We hypothesized that ionizing radiation exposure would compromise progenitor cell function leading to changes in their capacity for epithelial maintenance. We assessed progenitor cell function and capacity for clonal expansion following exposure to either X-rays or 56Fe using genetic lineage tracing in combination with in vitro and in vivo assays. We found that progenitor cells were lost in a radiation dose and quality-dependent manner, but surviving progenitor cells undergo significant clonal expansion for epithelial maintenance. Based on our data, we propose a model in which radiation induces a dose-dependent decrease in the pool of available progenitor cells, leaving fewer progenitors able to maintain the airway long-term.

Understanding Cancer Development. Processes after HZE-Particle Exposure: Roles of ROS, DNA Damage Repair, and Inflammation

Sridharan, D. M., Asaithamby, A., Bailey, S. M., Costes, S., Doetsch, P. W., Dynan, W., Kronenberg, A., Rithidech, K. N.,Saha, J., Snijders, A. M., Werner, E., Wiese, C., Cucinotta, F.A. and Pluth, J. M. Radiat. Res. 183, 1–26 (2015). 
Summary: 
Oxidative stress appears to play a central role in DNA damage, telomere dysfunction and inflammation as redox reactions regulate several critical biological processes. We have attempted to clarify how redox regulation is central in influencing biological response, cell fate and potentiating cancer risk especially in cells exposed to space radiation. This review summarizes our current understanding of some critical areas within the DNA damage and oxidative arena that are key aspects to more fully elucidate in order to obtain useful robust tools to accurately model cancer risk.

Effect of Radiation Quality on Mutagenic Joining of Enzymatically-Induced DNA Double-Strand Breaks in Previously Irradiated Human Cells. Radiation Research:

Zhentian Li, Huichen Wang, Ya Wang, John P. Murnane, and William S. Dynan (2014) November 2014, Vol. 182, No. 5, pp. 573-579.
Summary:   
Prior work has shown that exposure of mammalian cells to HZE-particle radiation predisposes them to inaccurately repair new DNA double-strand breaks induced experimentally at various times during recovery. The effect was seen originally when a human tumor reporter cell line was exposed to 600 MeV/u 56Fe particles (LET = 174 keV/micron), then challenged by expression of the rare-cutting endonuclease, I-SceI. HZE particle irradiation increased the frequency of I-SceI-mediated deletions and translocations relative to non-irradiated, or low-LET irradiated, controls. Here, we tested two additional ions, 1000 MeV/u 48Ti (LET = 108 keV/micron) and 300 MeV/u 28Si (LET = 69 keV/micron). Exposure to 48Ti increased the frequency of translocations, but not deletions, whereas the 28Si ions had no measurable effect on either endpoint. There was a close correlation between the induction of the mutagenic repair phenomenon and the frequency of micronuclei in the targeted population, whereas there was no apparent correlation with radiation-induced cell inactivation. Together, results better define the radiation quality dependence of the mutagenic repair phenomenon and establish its correlation, or lack of correlation, with other endpoints.

Impact of breathing 100% oxygen on radiation-induced cognitive impairment.

Wheeler K, Payne V, D' Agostino R, Walb M, Munley M, Metheny-Barlow L, Robbins M. Radiation Research: November 2014, Vol. 182, No. 5, pp. 580–585
Summary:   
Astronauts are exposed to space radiations while breathing 100% oxygen during an EVA. Given that brain irradiation can cause cognitive impairment and oxygen is a potent radiosensitizer, astronauts may have a greater risk of developing radiation-induced cognitive impairment during an EVA. In this study, unanesthetized and unrestrained rats were whole-body irradiated with 18 MV X-rays at a low dose rate of ~425 mGy/min while breathing either air or 100% oxygen for 30 min before, during and 2 h postirradiation. Within the study's limitations, breathing 100% oxygen under simulated EVA conditions, increased rather than decreased, cognitive function at all doses when compared to irradiated air-breathing rats. Thus, astronauts are not likely to be at a greater risk of developing cognitive impairment when exposed to space radiations while breathing 100% oxygen during an EVA.

 Does the worsening galactic cosmic radiation environment observed by CRaTER preclude future manned deep space exploration?

N. A. Schwadron, J. B. Blake, A. W. Case, C. J. Joyce1, J. Kasper, J. Mazur, N. Petro, M. Quinn, J. A. Porter, C.W. Smith, S. Smith, H. E. Spence, L.W. Townsend, R. Turner, J. K.Wilson, and C. Zeitlin. Space Weather (online), 11, doi:10.1002/2014SW001084
  
Data from a cosmic ray telescope onboard NASA's Lunar Reconnaissance Orbiter show that while increasing fluxes of cosmic rays "are not a show stopper for long duration missions (e.g., to the Moon, an asteroid, or Mars), galactic cosmic radiation remains a significant and worsening factor that limits mission durations.” 

Cosmic rays are intensifying. Galactic cosmic rays are a mixture of high-energy photons and subatomic particles accelerated to near-light speed by violent events such as supernova explosions. Astronauts are protected from cosmic rays in part by the sun: solar magnetic fields and the solar wind combine to create a porous 'shield' that fends off energetic particles from outside the solar system. The problem is "The sun and its solar wind are currently exhibiting extremely low densities and magnetic field strengths, representing states that have never been observed during the Space Age. As a result of the remarkably weak solar activity, we have also observed the highest fluxes of cosmic rays in the Space Age." 

The shielding action of the sun is strongest during solar maximum and weakest during solar minimum. At the moment we are experiencing Solar Max, which should be a good time for astronauts to fly. However, the solar maximum of 2011-2014 is the weakest in a century, allowing unusual numbers of cosmic rays to penetrate the solar system. 
This situation could become even worse if, as some researchers suspect, the sun is entering a long-term phase of the solar cycle characterized by relatively weak maxima and deep, extended minima. In such a future, feeble solar magnetic fields would do an extra-poor job keeping cosmic rays at bay, further reducing the number of days astronauts can travel far from Earth.

NCRP Commentary No. 23, Radiation Protection for Space Activities: Supplement to Previous Recommendations.

National Council on Radiation Protection and Measurements. Bethesda, MD.  November 18, 2014.
Summary:

This Commentary supplements previous recommendations from NCRP that underlie the current National Aeronautics and Space Administration (NASA) standards for radiation protection of crew members during space activities. This Commentary focuses on the implications of extended LEO missions in a general manner, particularly with regard to uncertainties in the knowledge of the health effects and the biological effectiveness of exposures to galactic cosmic rays in space, and includes a discussion of ethical considerations and principles that may bear on the application of NCRP advice on radiation protection for space activities. The Commentary is available from the NCRP website .

Densely Ionizing Radiation Acts via the Microenvironment to Promote Aggressive Trp53 Null Mammary Carcinomas.

Illa-Bochaca I, Ouyang H, Tang J, Sebastiano C, Mao JH, Costes SV, Demaria S, Barcellos-Hoff MH. Cancer Res. 2014 Oct 10. pii: canres.1212.2014.
Summary:  
Ionizing radiation is a complete carcinogen, able to both initiate malignant transformation by causing mutations in cells and to promote cancer progression by acting systemically via the tissue microenvironment.   Here, the authors use a radiation mammary chimera, in which the host is irradiated but the mammary epithelium is not, to demonstrate that densely ionizing radiation (350 MeV/amu Si) acts via the microenvironment to promotes development of aggressive mammary tumors.  Compared to sham-irradiated mice, a class of hormone receptor negative tumors grew faster and were more metastic in Si-particle irradiated mice. This study suggests that the response of tissues to densely ionizing radiation is an important component of its carcinogenic action;  unlike mutations per se,  the response of the microenvironment is amenable to countermeasures. 

New tricks for an old fox: impact of TGFβ on the DNA damage response and genomic stability.

M. H. Barcellos-Hoff, F. A. Cucinotta, (2014) Sci. Signal. 7, re5.
Summary:  
Transforming growth factor beta is a pleiotropic growth factor necessary for homeostasis and responses to injury.  TGFbeta activity is controlled by its secretion as a latent complex that is extracellularly activated by reactive oxygen species, engendering rapid and persistent mediation of tissue responses to radiation.   Here, the authors review how TGFb signaling is also involved in the efficient execution of the DNA damage response, which ties the intrinsic molecular mechanisms maintaining DNA integrity to extrinsic control of tissue function. 

Induction of Chromosomal Aberrations at Fluences of Less Than One HZE Particle per Cell Nucleus. Megumi Hada, Lori J.

Chappell, Minli Wang, Kerry A. George, and Francis A. Cucinotta (2014) Radiation Research: October 2014, Vol. 182, No. 4, pp. 368–379.
Summary:  
We investigated the dose response for chromosomal aberrations for exposures corresponding to less than one particle traversal per cell nucleus by high-energy charged (HZE) nuclei. Nonlinear regression models were used to evaluate possible linear and nonlinear dose-response models based on these data. Dose responses for simple exchanges for human fibroblasts were best fit by nonlinear models motivated by a nontargeted effect (NTE). The best fits for dose response data for human lymphocytes were a linear response model for all particles. Our results suggest that simple exchanges in normal human fibroblasts have an important NTE contribution at low-particle fluence. The current and prior experimental studies provide important evidence against the linear dose response assumption used in radiation protection for HZE particles and other high-LET radiation at the relevant range of low doses.

Description and Verification of an Algorithm for Obtaining Microdosimetric Quantities for High-LET Radiation Using a Single TEPC without Pulse Height Analysis.

Thomas B. Borak and Phillip L. Chapman (2014) Radiation Research: October 2014, Vol. 182, No. 4, pp. 396–407.
Summary: 
Microdosimetric spectra of single event distributions have been used to provide estimates of quality factors for radiation protection of high LET radiation.  It becomes difficult to measure, record and store energy deposition from single events in situations with high dose rates.  An alternative approach is to store random energy deposition events in a sequence of fixed time intervals that does not require recording single events.  This can be accomplished with one detector without pulse shaping or pulse height analysis.  We present the development of the algorithm using expectation analyses of the statistical estimators for moments of lineal energy.  The method can provide prompt real-time information in circumstances that restrict detector configurations in terms of size, mass and power consumption such as personal dosimetry during an EVA.  It can be adapted for measurements of any quantity that is linearly related to absorbed dose, such as estimation of dose averaged LET.

Radiation Quality and Mutagenesis in Human Lymphoblastoid Cells. Radiation Research

Howard L. Liber, Rupa Idate, Christy Warner, and Susan M. Bailey (2014) October 2014, Vol. 182, No. 4, pp. 390–395.
Summary:
 
It seems logical that after exposures to low doses of HZE particles, damage to individual cells should be distributed as described by Poisson statistics.  Cells with the most traversals and thus the highest probability of experiencing induced mutations would also be more likely to grow slowly during the expression period; these cells would be “diluted” by more rapidly growing, less damaged cells.  This would lead to an underestimation of the actual level of induced mutations.  In the manuscript, we showed that this was true, and went on to characterize induced mutations as a function of radiation quality — silicon at 400 MeV/n was the most mutagenic ion/energy.  Interestingly, we found that induction of non-targeted mutagenesis had a pattern which appeared to be the mirror-image of that seen for direct effects.

Updates to Patrick M. O’Neill’s NASA Space Radiation Summer School Lecture The Natural Ionizing Space Radiation Environment have been posted to the THREE Encyclopedia -- Basic Concepts of Space Radiation.
Posted November 7, 2011

Mary Helen Barcellos-Hoff’s NASA Space Radiation Summer School lecture Systems Radiation Biology and Radiation Induced Cell Signals has been posted to the THREE Encyclopedia – Tissue Biology and Pathology.
Posted November 3, 2011

Congratulations to space radiation investigators Francis Cucinotta and Sylvain Costes, who have been elected Vice-President-Elect and Physics Councilor, respectively, for the Radiation Research Society.
Posted to the Archive, November 7, 2011.

Revisions to the NASA projection model for lifetime cancer risks from space radiation and new estimates of model uncertainties are described in NASA/TP-2011- 216155, Space Radiation Cancer Risk Projections and Uncertainties – 2010 by Francis A. Cucinotta, Myung-Hee Y. Kim, Lori J. Chappell.
Posted October 17, 2011

The article Acute Effects by Thomas M. Seed has been newly revised and is posted in the Health Effects section of the THREE Encyclopedia.
Posted to the Archive October 20, 2011.

Science Now reports a new study suggesting “worse space weather” – with more threats to astronauts -- during the next decades:
Posted September 26, 2011.

Updates to Astronaut Radiation Limits: Radiation Risks for Never-Smokers was published online by Rad Res, May 16, 2011.  The article from the Space Radiation Program Laboratory at NASA Johnson Space Center recommends dose limits for astronauts that take into consideration age- and gender-specific dose limits for never-smokers. 
  Posted May 27, 2011.

On April 21, 2011, the International Commission on Radiological Protection (ICRP) issued new recommendations on radiological protection.  The Commission has now reviewed recent epidemiological evidence suggesting that there are some tissue reaction effects, particularly those with very late manifestation, where threshold doses are or might be lower than previously considered. For the lens of the eye, the threshold in absorbed dose is now considered to be 0.5 Gy. Accordingly, (3) For occupational exposure in planned exposure situations the Commission now recommends an equivalent dose limit for the lens of the eye of 20 mSv in a year, averaged over defined periods of 5 years, with no single year exceeding 50 mSv. In part, the new recommendations are based on research reported by NASA scientists:

The full draft report may be found at  Annals of the ICRP.


A new text by Dr. Olga Smirnova, Environmental Radiation Effects on Mammals: A Dynamical Modeling Approach , has been published by Springer. Read more. Posted to the Archive, May 27, 2011.

Feature article on Radiation Risk in Technology Innovation, NASA's magazine for Business & Technology, Volume 15 Number 3, 2010. Posted to the Archive, May 17, 2011.

Mitigating Astronauts' Health Risks from Space Radiation
Francis A. Cucinotta, Ph.D.

NASA Space Radiation Summer School Slide Notes Competition

2013 Slide Competition

2012 Annual NASA Space Radiation Summer School Slide Competition

2011 Annual NASA Space Radiation Summer School Slide Competition

2010 Annual NASA Space Radiation Summer School Slide Competition