1022-7954/02/3810- $27.00 © 2002
Russian Journal of Genetics, Vol. 38, No. 10, 2002, pp. 1140–1144. Translated from Genetika, Vol. 38, No. 10, 2002, pp. 1345–1350.
Original Russian Text Copyright © 2002 by Osipov, Elakov, Puchkov, Pomerantseva, Ramaiya, Klokov, Sypin, Shevchenko.
Unlike high dose-rate ionizing radiation (IR), which
has undoubtedly an adverse effect on the organism, the
question of whether low dose-rate IR is harmful
remains unclear. According to the published data of
many authors [1–3] and our studies [4, 5], low-dose
ionizing radiation induces a series of biochemical and
biophysical reactions in the animal organism. However,
it remains unknown whether these changes appear as a
result of the organism adaptation to an increased radia-
tion background and whether the low-dose irradiation
leads to signiﬁcant genetic consequences.
In this study, we aimed at determining the level of
DNA–protein crosslinks (DPC) and DNA breaks in spleen
lymphocytes, the percentage of micronucleated normo-
chromatic erythrocytes (NCE) in the peripheral blood, and
the frequency of abnormal sperm heads (ASH) in mice
exposed to long-term low dose-rate
The choice of a dose of
-radiation was based on the
results of radiological monitoring in various Russian
areas polluted after the Chernobyl disaster.
MATERIALS AND METHODS
The 4-week-old male CBA/lac mice weighing 12 to
14 g were obtained from the Stolbovaya breeding facility,
Russian Academy of Sciences. Seven days before the
exposure to radiation, the animals were maintained in
plastic cages. Both the experimental and control groups
contained randomly sampled animals. Mice were given
standard food and water. The control and experimental
animals were maintained under identical conditions
10% relative humidity, 12-h illumination).
Mice were irradiated in a UOG-1 device (a source of
Cs], 0.17 cGy/day dose rate) for 40, 80, 120, 210,
and 365 days to expose the animals to the doses of 6.8;
13.6; 20.4; 35.7; and 63.5 cGy, respectively. For radia-
tion monitoring, either thermoluminescent detectors
TLD-100 (Sweden) and DTG-4 (Russia) or devices
RE-1 (RADOS, Finland) and DTF (Russia) were used.
The animals were decapitated on days 40, 80, 120,
210, and 365 and the spleen and testes were withdrawn.
The spleen cell suspension in a phosphate-salt
buffer containing 10 mM phosphate buffer, pH 7.4,
0.14 M NaCl, 2.7 mM KCl, and 3 mM NaN
cooled to 4
C and ﬁltered through a nylon gauze. The
cell count was determined using Goryaev’s chamber.
The DPC number was determined by the method of
detergent precipitation  modiﬁed as described in .
A single-cell microgel electrophoresis under alka-
line conditions was conducted as described by Singh
. According to this method, the number of the
single-stranded DNA breaks is in direct proportion to
the DNA amount and the extent of its migration from
the nuclear region after alkaline electrophoresis of indi-
vidual cells embedded in agarose. The Hoechst 33258
ﬂuorescent dye was used for staining. The DNA “com-
ets” were examined on a Lumam I-2 (LOMO, Russia)
ﬂuorescent microscope. A hundred of comets was
counted on every slide. Depending on the appearance
The Estimation of Molecular and Cytogenetic Effects
in Mice Exposed to Chronic Low Dose-Rate Gamma-Radiation
A. N. Osipov
, A. L. Elakov
, P. V. Puchkov
, M. D. Pomerantseva
, L. K. Ramaiya
D. Yu. Klokov
, V. D. Sypin
, and V. A. Shevchenko
Moscow Research and Industrial Association–Joint Ecological Technological, and Research Center
for the Radioactive Waste Decontamination and Environmental Control (Radon), Moscow, 119121 Russia;
fax: 248-19-41; e-mail: email@example.com
Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119991 Russia;
: 135-89-62; e-mail: Shevchenko@vigg.ru
Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, 142292 Russia;
: (0967) 79-05-53
Received December 11, 2001; in ﬁnal form, January 29, 2002
—Molecular and cytogenetic parameters were estimated in male CBA/lac mice exposed to chronic
-radiation (62 cGy/year) for 40, 80, 120, 210, and 365 days. After 40 days of exposure (6.7 cGy),
spleen lymphocyte susceptibility to hydrogen peroxide was shown to increase. However, beginning from the
day 120 of the treatment (20.4 cGy), the opposite effect was observed. An increase in number of the DNA–
protein crosslinks was recorded in spleen lymphocytes only on day 40 of the experiment. The number of DNA
breaks increased signiﬁcantly beginning from day 120 of the experiment, as shown by the DNA-comet method.
On the day 210 of irradiation, the frequency of abnormal sperm heads in the mice signiﬁcantly increased. The
number of normochromatic micronucleated erythrocytes of the peripheral blood remained unchanged.