Probability of cell hits in selected organs and tissues by high-LET particles at the ISS orbit

Radiation damage to neuronal cells: Simulating the energy deposition and water radiolysis in a small neural network

Radiation damage to the central nervous system (CNS) has been an on-going challenge for the last decades primarily due to the issues of brain radiotherapy and radiation protection for astronauts during space travel. Although recent findings revealed a number of molecular mechanisms associated with radiation-induced impairments in behaviour and cognition, some uncertainties exist in the initial neuronal cell injury leading to the further development of CNS malfunction. The present study is focused on the investigation of early biological damage induced by ionizing radiations in a sample neural network by means of modelling physico-chemical processes occurring in the medium after exposure. For this purpose, the stochastic simulation of incident particle tracks and water radiation chemistry was performed in realistic neuron phantoms constructed using experimental data on cell morphology. The applied simulation technique is based on using Monte-Carlo processes of the Geant4-DNA toolkit. The calculations were made for proton, ¹²C, and ⁵⁶Fe particles of different energy within a relatively wide range of linear energy transfer values from a few to hundreds of keV/μm. The results indicate that the neuron morphology is an important factor determining the accumulation of microscopic radiation dose and water radiolysis products in neurons. The estimation of the radiolytic yields in neuronal cells suggests that the observed enhancement in the levels of reactive oxygen species may potentially lead to oxidative damage to neuronal components disrupting the normal communication between cells of the neural network.

Analysis of cell cycle in mouse bone marrow cells following acute in vivo exposure to 56Fe ions

A pilot study was conducted to examine the magnitude of cell-cycle delay and apoptosis in bone marrow (BM) cells collected at 18, 42 and 66 hr from radiosensitive CBA/CaJ mice and radioresistant C57BL/6J mice following a whole-body in vivo exposure to 1 GeV/amu (56)Fe ions or (137)Cs gamma rays. At each sacrifice, BM cells were collected from three mice of each strain per dose of (56)Fe ions (0, 10 and 100 cGy) and two mice of each strain per dose of (137)Cs gamma rays (0, 100 and 300 cGy). A significant G1-arrest (ANOVA, p < 0.05) was observed at 18 hr after exposure of mice to 100 cGy of (56)Fe ions or 300 cGy of (137)Cs gamma rays, relative to their corresponding sham-controls, resulting in a significant decrease in the percentage of cells cycling into S-phase in both strains. The percentage of S-phase cells subsequently increased and persisted up to 66 hr post-irradiation. Significant numbers of G2/M cells were found at 18 and 66 (but not at 42) hr post-irradiation, regardless of radiation-type or mouse-strain. It is likely that BM cells have undergone at least one cell cycle at 66 hr after exposure of mice to either 100 cGy (56)Fe ions or 300 cGy (137)Cs gamma rays. Our study is the first to investigate the in vivo effects of (56)Fe ions (1 GeV/amu) on the cell cycle of mouse BM cells using flow cytometry. The cell-cycle distribution (but not the number of apoptotic cells) was dependent on radiation-dose and harvest-time.