Chromosome-2, a European Space Agency experiment, is a continuation of the Chromosome investigation performed on earlier ISS expeditions. White blood cells (lymphocytes) are collected from crewmembers preflight and postflight. The lymphocytes are examined using different analytic methods to determine quantity and quality of genetic changes resulting from exposure to cosmic radiation, particularly ionizing radiation.Principal Investigator(s)
European Space Agency (ESA), Noordwijk, , Netherlands
European Space Agency (ESA)Sponsoring Organization
Information PendingResearch Benefits
Information PendingISS Expedition Duration:
October 2005 - April 2008Expeditions Assigned
12,13,14,15,16Previous ISS Missions
Earlier versions of this experiment flew on the Space Shuttle and the Russian Space Station, Mir, as well as, ISS Expeditions 6-11.
Cosmic radiation is a major risk factor in manned space missions. This investigation will give a better insight into the mutagenic burden of astronauts during space flights as consequence of exposure to the complex cosmic radiation field. Although it can be assumed that radiation plays a major role in mutation induction in astronauts, synergistic influences such as weightlessness, acceleration, vibration hyperthermia, noise microwave radiation, physical exercises, trauma, and infections cannot be ruled out.
During flights astronauts are chronically exposed to radiations of solar and galactic origin. The space radiation field consists of electrons, protons, heavy particles, and secondary radiation like bremsstrahlung, neutrons, and charged particles created by interactions of primary radiations with nuclei of spacecraft shielding material or the human body (Reitz et al., 1996). The contribution of the dose of single radiation types depends on altitude and inclination of the spacecraft, effective shielding thickness and solar activity during the mission.
Information PendingEarth Applications
Information PendingOperational Protocols
The Chromosome-2 experiment will use astronauts as test subjects, but no actual in-flight experiment or data collection will be carried out. To assess the genetic impact of space radiation, blood (15 mL) is drawn before and directly after flights by venous puncture. Whole blood cultures will be set up with phytohemagglutinin to stimulate lymphocytes to undergo mitoses. After 48 h mitotic cells will be arrested with Colcemid, fixed and prepared on slides for microscopic analysis. The preparations will be scored for chromosomal aberrations. Three different staining procedures shall be performed to assess all types of aberrations induced by ionising radiations:
As astronauts spend longer periods in space, it has become more important to accurately measure radiation doses and assess individual risk for long-duration space flights. Chromosome damage in peripheral blood lymphocytes, a type of white blood cell (WBC), is commonly used as an indicator of radiation exposure, and the introduction of the fluorescence in situ hybridization (FISH) chromosome painting technique has made it possible to "paint" individual chromosomes with different colors so alterations can be identified as multi-color chromosomes allowing for more detailed and accurate analysis.
NASA has implemented a radiation biodosimetry program that utilizes FISH to determine chromosomal damage in US astronauts who participate in long-duration missions. All crewmembers returning from ISS missions are evaluated for chromosomal damage in lymphocyte cells with this technique. For this study, physical and biological doses for 23 ISS astronauts yielded average effective doses and individual or population-based biological doses for the approximately 6-month missions of 85 or 81 mGy-Eq (milligray-equivalent), respectively, which is well below NASA limit of 250 mGy-Eq per 30 days. For comparison, the average radiation dose from a chest X-ray is < 0.25 mGy. Analyses showed that galactic cosmic rays (GCR) is the major source, responsible for 80% or more, of radiation organ dose absorbed on the ISS. Comparisons of models to clinical data showed that space radiation effective doses can now be predicted to within about a +15% accuracy (George et al., 2011, Cucinotta et al., 2008).
Early chromosome studies strongly indicated that the radiation dose absorbed during a long-duration flight can cause quantifiable increases in chromosome damage, whereas shorter missions of a few weeks or less did not show measurable effects. These previous studies focused on the detection of dicentric chromosomes (2 partial chromosomes joined at broken ends resulting in a chromosomal structure having 2 distinct pinched areas called centromeres) which are known to decay over time with an average half-life of about 3 years, but more recent studies indicate that this rate of decay could vary greatly between individuals (Durante, 2005). In addition, follow-up measurements of chromosome damage in the blood lymphocytes by FISH from 5 months to more than 5 years after space flight revealed a time-dependent loss of "stable?" aberrations as well in blood lymphocytes, with half-lives ranging from 10 to 58 months. Current available data show that biodosimetry analyses on samples collected within a week or two of return from space provides a reliable estimate of equivalent radiation dose and risk after exposure to space radiation of a few months or more. However, retrospective doses may be more difficult to estimate because of the fairly rapid time-dependent loss of "stable" chromosomal aberrations in blood lymphocytes. Also, biodosimetry estimates from individuals who participate in repeated missions, or very long (interplanetary) missions, may be complicated by an adaptive response to space radiation and/or changes in lymphocyte survival and repopulation (George et al., 2005, 2007).
Radiation exposure for missions beyond low earth orbit will be much greater because of the absence of the magnetic protection provided by the Earth. Understanding the biological effects of such exposures and developing effective countermeasures is a major endeavor and is the focus of current international research efforts (Cucinotta, 2011).
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