Chapter I
PREGNANCY EVOLUTION, FETUS AND NEWBORN
DEVELOPMENT DURING ENDOGENOUS RADIATION
INCORPORATION
The problem of ionizing radiation effect upon the human organism bas
been an ambitious task since the Chernobyl disaster. It is a current specific
feature that ionizing radiation chronically affects the organisms of humans and
animals through its incorporation with food. During recent years the disaster
effects already touch greater contingents of people exposed to the ionizing
radiation.
These conditions render the population group of
pregnant women and infants critical [1,15,17]. Extensive research has been
accomplished to get insight into the problem how radioactive exposure affects
pregnancy, fetus and newborn development [3-5, 9, 13, 14]. It bas been revealed
that the embryo is specifically vulnerable during critical “periods” when this
or that systems undergoes differentiation. Chronic exposure is particularly
risky affecting various types of embryonic cells damaging a great number of
germinal organs during such critical periods of their development, very small
doses of ionizing radiation causing the maximum injury. Among other products of
nuclear fission released by Chernobyl 137Cs and 90Sr
having a long half life period are most detrimental for the biological chain.
Hence small doses of these radionuclides are continuously incorporated by
living organisms with food.
So far there is insufficient insight into the effects of small doses of
chronic endogenous incorporation of 137Cs and 90Sr upon
the processes of prenatal and postnatal development. The objective of
the present study is a comprehensive morphofunctional investigation of the
features of prenatal and postnatal development of common white rats when these
radionuclides are incorporated with the components of their diet.
The major objectives of the study are the following:
1. To investigate the features of prenatal development of common white
rats during endogenous incorporation of radionuclides (137Cs and 90Sr)
with food.
2. To reveal
the features of postnatal development of common white rats during endogenous
incorporation of radionuclides (137Cs and 90Sr) with
food.
3. To
investigate the pattern of accumulation of 137Cs during its endogenous
incorporation with grain by the mother and the offspring.
4 To reveal
possible metabolic changes in the organism of female white rats in pregnancy
during endogenous incorporation of radionuclides (137Cs and 90Sr)
with food.
The study
covered 137 pregnant female common white rats, 745 embryos and 344 infant rats.
The first day the sperm would be found in vaginal smears was assumed the
pregnancy start. The animals were kept in the vivarium. The fetuses were
extracted on the 20th day of intrauterine development because by this time the
orthogenesis and placenta evolution would be completed
In order to investigate the features of prenatal
and postnatal development the animals were kept on a diet providing a daily
incorporation of radionuclides (beef and oats). The concentration in the food
(meat and grain) for the diet of the control and test animals is shown in Table
1.1.
The daily
incorporation of radionuclides by pregnant rats was estimated based on the
food consumption (Table 1.2).
Therefore, the food radioactivity
was primarily rated based on 137Cs.
The test and control animal groups
to investigate prenatal and postnatal development were determined based on the
qualitative composition of the diet (beef meat or oats) and the concentration
of radionuclides (Table 1.3)
The following
techniques were applied to achieve the objectives:
1. The
method of Wilson modified by A.P. Dyban (A.P. Dyban et al., 1970) to
investigate the condition of internal organs of fetuses.
In order to
evaluate the condition of internal organs and the brain the embryos fixed in
the Buen mixture were placed on a paraffin table and e series of parallel
sections were made with a razor.
2. The Dowson method modified by A.P. Dyban 16]
to investigate the bony skeleton of rat fetuses. The size of skeletons (the
pariet-to-coccygeal size) was measured with compasses. The ossification
analogue sire was measured with the help of an ocular micrometric microscope
(MPC-10, ocular 8, magnification 2).
3. A
common technique for hemoglobin, erythrocyte, leucocyte count and the
leucocytary formula.
4. Measurement
of 137Cs accumulation in the mother and the offspring. The 137Cs
concentration in female common white rats during pregnancy and lactation and in
the offspring during lactation was checked in vivo based on ³-emission
using a gamma-radiometer L - 92.
5. A
“Synchron” analyzer produced by Beckman (USA) served to evaluate biochemical indicators
of the blood serum of pregnant rats.
6. Evaluation
of 137Cs and 90Sr concentration in food was performed
using spectrometric anti radiochemical technique of the (Gomel Regional
Sanitation and Hygiene Center. The variational statistics technique was used
for data processing.
The study has revealed that in case
female white rats since the 1st day of pregnancy are kept on a diet of meat
with the 137Cs concentration 5587 Bq/kg and 90Sr
23.7 Bq/kg there is a valid increase of preimplantation death — 2.27 ± 0.52 (p
<0.05). Consumption of grain with 137Cs concentration 445.7Bq/kg, 90Sr — 15.5 Bq/kg by pregnant rats would no produce
any essential preimplantation death rate compared with the control group. The
postimplantation death rate in the two test group corresponded to the control.
The data about higher
preimplantation death rate during radioactive exposure correlate with other
reported data about the death rate of fetuse during this period [16,18] The
analysis of publications indicates that radiation during the preimplantation
period induces more frequent mutations of two types or mutations of genes and
chromosomes. The genetic mutations hill the zygote. non-lethal mutations may be
the cause of monsters [12].
The study has revealed that mothers
alter dieting during pregnancies on meat and grain with a higher 137Cs
and 90Sr concentration in the test group would have an offspring
with a valid reduction of the average size of bony skeletons (the
panet-to-coccygeal size) compared with the relevant control (Table
1.4).
The mothers alter dieting on meat
with a higher 137Cs and 90Sr concentration would have an
offspring with the valid absence of the anlages of ossification of metacarpal
and metatarsal bancs compared with the control. No significant difference
between the test and control offspring if mothers would diet during pregnancy
on the grain (Table 1.4).
Investigation of the condition of
bony skeletons of the test fetuses after feeding mothers with the meat
containing ‘3’Cs bas revealed a valid symmetrical hypoplasia of the
anlages of ossification of ail the bancs manifested to different extent, the
bilateral absence of anlages of pubic bones, absence of points of ossification
of the 2nd and 4th metacarpal bones. 2nd, 3rd and 4th metatarsal bones (Fig.
11).
Similar studies of bony skeletons of
test fetuses born by mothers alter dieting with a higher 137Cs and 90Sr
concentration in the grain has revealed a valid bilateral reduction OF the size
of anlages of ossification of all the bones, excepting the 4th metacarpal and
2nd and 3rd metatarsal bancs (the difference with the control group is
insignificant). Also a bi-lateral absence of anlages of pubic bones, the 2nd
metacarpal, the 4th metatarsal bones (Fig. 1.2) were found.
Evaluation of the results and
comparison with the reported data allow to assume that
the major causes of misformation of the bony system
among white rat fetuses can be n disordered inductive interaction between the
somato-pleural mesoderm and the coating endoderm or the death of mesenchymal
ceils caused by the incorporated 137Cs. Another possible cause may be the
abnormalities occurring during separate stages of the bone tissue morphogenesis
[8].
The 45-day old offspring of
the mothers after the meat diet with a higher radiation concentration
manifested valid reduction of leucocytes 6.27 ± 0.75 x 10 /1 (p <
0.05), lymphocytes 72.38 ± 3.35% (p < 0.02) in the peripheral blood against
the increased eosinophil count 2.63 ± 0.65% (p <0.05) compared with
the control group.
Daily 137Cs incorporation
by female rats since the lst day of pregnancy and throughout the lactation
period with oats containing 445.7 Bq/kg would result in its significant
accumulation in the mother’s organism. The offspring would not manifest any
pronounced accumulation of 137Cs (Fig. 1.3).
Similar dynamics was manifested by the
control group also when oats contained 44.2 Bq/kg of 137Cs, but it
was less pronounced. The 137Cs concentration among the test female
rats by the end of pregnancy was 132.77 ± 10.77 Bq/kg and the control rats had
9.22 ± 2.90 Bq/kg. The test offspring had the 137Cs concentration
6.47 ± 2.18 Bq/kg, the control group had 1.61 ±0.87 Bq/kg (Fig. 1.4).
Persistent differences in the 137Cs
accumulation between the test and control female rats at the end of pregnancy
and during lactation can probably be explained by the fact that the 137Cs
absorption is stimulated resulting in its growing accumulation in the mother’s
organism.
