Attachment 7
Research on the Biological Effect of Heavy Charged Particles with Different Energies
For over 50 years biological experiments have been held at charged particle accelerators
in the Joint Institute for Nuclear Research (JINR). The start of the research was connected with
the exploration of the near-Earth space environment and provision of radiation safety for Man in
the outer space. This kind of research was aimed at the studies of the biological action produced
by different types of space radiation and, primarily, by high energy protons. When first space
flights with animals and man were prepared it was not clear how living organisms would behave
in the conditions of the multi-component radiation action, including that of high energy protons
which are generated by the Sun and come from the depth of the Galaxy.
It became possible to solve this task in the ground conditions, irradiating biological
objects at the first accelerator of Dubna that generated high energy proton beams. At the
initiative and support of Academicians A.V. Lebedinsky, V.V. Parin, O.G. Gazenko, extensive
experiments were started at JINR to determine biological efficiency of high energy protons, and
these studies made it possible to provide radiation protection for the crews in the first space
flights. Thus, Dubna has made a weighty contribution to the exploration of the near-Earth space
environment.
Subsequently, radiobiologists of JINR, in collaboration with specialists from our country
and other member states of the Institute, continued these studies. In 1978, the Sector for
biological research was established; it conducted research in fundamental issues of general and
space radiobiology: its aims were to study the mechanisms that specify the distinctions in
biological efficiency of ionizing radiation with different physical characteristics, to investigate
fundamental processes that lie at the root of the mutagenic action produced by accelerated
charged particles of high energy. Since 2005 this research has been conducted at the Laboratory
of Radiation Biology – a new JINR division that overlapped studies of biological action of
ionizing radiation and radiation protection.
At present, research is conducted at JINR for the multipurpose studies of regularities and
mechanisms of the action produced by heavy charged particles on the molecular, cell, tissue and
organism levels of the biological organization. Studies are continued of the formation
peculiarities of cluster DNA double-strand breaks – the most severe damage in genetic structures
at the action of heavy charged particles. As it is known, these types of damage lie at the root of
the cell death, formation of various mutations, cell malignant transformations. Research is
conducted of the action of the low-dose radiation types on the cell level.
The studies in the field of radiation physiology are of particular interest, as they are
concerned with the issues of the influence cast by heavy charged particles on the eye retina, the
structure and functions of the central nervous system. These elaborations are exclusively urgent
for the solution of tasks in space radiobiology. The recently obtained data on the development of
radiation syndromes at the action of heavy charged particles on the brain structures that lead to
its integrity breach afford ground to regard the central nervous system as a “critical” one in
evaluating the risk of radiation action on the space crewmembers’ organisms in interplanetary
flights.
The topics of such research are quite new. Many responses of the central nervous system
to the radiation influence, both on the cell and organism levels, still remain unexplored. At the
present time, scientists of the Laboratory of Radiation Biology together with specialists from
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other Russian institutions hold multipurpose research aimed at the studies of the central nervous
system response to the action of ionizing radiation.
A series of experiments have been held so far at the Dubna accelerators of heavy nuclei
to investigate separate neurochemical mechanisms that may be at the heart of changes in
behaviour and memory impairment that are observed in small laboratory animals in early and
long term periods of time after irradiation. The report “Early and long-term effects of low- and
high-LET radiation on the rat behavior and the monoamine metabolism in different brain
regions” (Belov et al.) that was registered for presentation at the 40th Scientific Assembly of
COSPAR will discuss the topic.
The studies conducted at Dubna ought to give information on the issue how dangerous is
the influence caused by heavy nuclei of the galactic cosmic radiation in any interplanetary,
including the one to Mars, mission. It is vital to find the answer to the question if impairments in
supreme integrative functions of the central nervous system will occur at the action of such a
unique radiation factor as heavy charged particles, whose character of energy transfer differs
drastically from the usual types of ionizing radiation (X-rays and gamma-rays). It is necessary to
find out to what extent these impairments will grow at the dramatic psychological strain that
inevitably will occur in the interplanetary flight.
In this context, the experiments with primates are important, as they allow the evaluation
of mainly behavioural and cognitive reactions that occur in different periods of time after
exposure to heavy charged particles. First experiments of this type are already under way in
Dubna, using carbon nuclei and protons of high energy. Such research is an important period of
extrapolation of the changes observed in laboratory animals onto Man.
One of the concluding results of the whole complex of scientific studies at the Laboratory
of Radiation Biology of JINR must be in the facts that make it possible for us to approach the
estimation of the risk in radiation action in the conditions of an interplanetary flight. The risk
concept used today of the nearest radiation-induced effects that can occur during the mission
considers mainly the impairment of the bone-marrow hemopoiesis, damage to skin and other
organs and tissues of the organism. The long-term effects of irradiation that can form during the
subsequent life period are traditionally related to the growth of tumour processes in the
organism. However, facts have been obtained that allow us to presume that the total radiation
risk for space crewmembers that is evaluated with an account for the growth of impairments in
other systems (the central nervous system, the vision system, the cardiovascular system, the
neuroendocrinal system, etc.) is several times bigger, in comparison with the progression of
tumour diseases. Thus, the research in this field will promote development of a principally new
concept of risk for crews of spaceships that will have in its basis the notion of probability for
successful accomplishment of the mission and possible formation of radiation damage, including
that in the physiological systems that have not be considered earlier in estimation of radiation
hazards during the mission.
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