Radiosensitivity of chromosome apparatus of voles from alienation zone of Chernobyl’s accident




Дата канвертавання22.04.2016
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Radiosensitivity of chromosome apparatus of voles from ALIENATION zone of Chernobyl’s accident.

Kovalova O.A.

Institute of agriecology and biotechnology UAAS, Kiev, Ukraine.

Traditionally small-sized rodents were used for bioindication of territory pollution by different gene toxic agents. Investigations of cytogenetic anomaly frequencies in somatic cells in connection with ionizing irradiation in the last 50 years were widely conducted on the people, plants, small-sized Rodentia species and others. The high individual variability in tested species in the same conditions, and also the absence of precise relations between quantity of cytogenetic damages in somatic cells and dozes of ionizing irradiation were the singularity of the accumulated data. It is not exclude, that one of cause of this result may be relate with both the peculiarities of species karyotype and morphology of individual chromosomes.

Materials and Methods

The different vole’s species were trapped in Chernobyl’s zone with various levels of radio nuclide pollution (20 – 100 - 1000 Cі/km2). Species differed by number of acrocentric and metacentric chromosomes in the karyotypes: Microtus arvalis (2n=46, Fna=84), Microtus subarvalis (2n=54, Fna=54), Clethrionomus glarealus (2n=56, Fna=56), Microtus oeconomus (2n=30, Fna=56), Microtus agrestis (2n=50, Fna=54). The preparations of bone marrow cells of representatives of vole’s species were obtained by standard technique without colchicine. It was analyzed 9 cytogenetic characters in bone marrow cells such as the frequency aneuploidy (which was evaluated in two variants: general aneuploidy (A1) and aneuploidy (A2) on one chromosome (2n±1)), polyploidy (PP), the frequency of metaphase plates with chromosome aberrations (CHA), interchromosome fusion on a type of Robertsonian translocation (RB), with asynchronous separation of centromere chromosome region (ASCR) (in %). Quantity of metaphase plates (MI) in 1000 cells, binuclear leukocytes (BL) and leukocytes with the micronuclei (LM) calculated on the same preparations in cells with saved cytoplasm (in ‰). Statistical reliability of between group differences was evaluated with use of Student criterion (tS).



Results and Discussion

In the zones with high-level radio pollution in all species of voles the increase of the mitotic activity and related with it the little decrease of metaphase frequency with asynchronous fission of centromeres (ASCR) were observed (tabl. 1).

In the zones with low-level radio pollution the specters of cytogenetic parameters had significant species peculiarities. For example, at the Microtus arvalis the frequency of aneuploidy cells was higher then at the other species. At the Clethrionomus glarealus the frequency of metaphases with interchromosome fusion on the type of Robertsonian translocation were met more often then at the Microtus arvalis (Fig.1).

In the cytogenetic anomaly specters of animals from Chernobyl’s zone with high-level radio pollution the increased frequencies of those cytogenetic anomalies which were unstable in the zones with low-level radio pollution (Microtus arvalis – aneuploidy, the voles with acrocentric autosomes – centric fusion of the chromosomes) were observed. The high frequency of chromosome inversions in group of little-sized chromosomes in Microtus agrestis (about 30% of metaphases) was revealed.

The participation of individual chromosomes in mutation spectra of some vole’s species was analyzed. The group of biggest chromosomes involved into aneuploidy with high frequency in the Clethrionomus glarealus but the same chromosomes participated with low frequency in asynchronous separation of centromere regions. However, in cells of Microtus oeconomus the chromosomes 10 and 14 preferable involved into aneuploidy and asynchronous separation of centromere regions.

Table 1. Spontaneous and induced mutation spectra in different species of voles



N

anim


N

met.


frequency of metaphases

on 1000 lymphocytes

А1

А2

PP

RB

CHA

ASCR

МI

BL

LM

Razezzhee (<5 Ci/km2 ) Microtus arvalis



















15

948

44,45,1

8,62,8

0,90,5

0,10,5

2,50,6

16,54,9

4,50,9

5,00,8

3,00,4

Chistogalovka (>500 Cі/km2)



















9

784

52,78,3

17,94,4

0

0,40,4

3,.60,8

3,70,7

10,00,6

7,90,3

6,80,5

Lelev (~ 20 Cі/km2) M. rossiaemeridionalis



















3

170

36,313,9

5,0 3,4

3,4 3,4

31,65,9

2,02,0

0,70,7

3,62,8

3,41,3

2,40,8

Nedanchichi (<5 Cі/km2) Clethrionomus glarealus



















4

97

33,76,0

9,03,5

14,03,5

1,50,5

1,20,7

6,23,6

3,20,6

3,50,6

5,51,5

Red forest (~1000 Ci/km2)






















3

252

33,70,9

5,02,1

3,73,7

5,73,3

7,33,4

2,31,9

10,31,9

7,01,0

9,31,9

Lelev (~ 20 Ci/km2) Microtus oeconomus



















4

370

21,26,4

4,21,4

1,70,8

0

2,70,9

12,73,3

3,70,2

8,02,1

4,50,9

Like Deep (500 Кі/км2)



















6

579

23,05,0

12,54,7

0

0

5,.00,9

1,80,7

9,80,6

7,.20,4

5,.50,6

Red forest (~ 1000 Ci/km2) Microtus agrestis



















2

124

25,08,5

3,9 3,6

0

16,111,9

9,71,4

21,711,6

1,50,5

1,80,2

2,80,2

In cells of Microtus arvalis the group of smallest chromosomes was preferable involved in aneuploidy, but the group of big chromosomes participated in it very rare. However the group of big chromosomes participated preferable in the asynchronous separation of centromere regions.

Conclusion

Our dates shows that spontaneous spectra (at the low-doze radio pollution) of cytogenetic anomalies in bone marrow cells are characterized by the species-specific traits in the voles both on predominance of cytogenetic anomalies (centric fusion – for species with predominance of acrocentric chromosomes, aneuploidy – for the Microtus arvalis, asynchronous separation of centromere regions – for the Microtus arvalis and Microtus oeconomus) and on involving into anomalies of the individual chromosomes also. In the Chernobyl’s zone the animals with constitutive chromosome aberrations did not revealed. The chronic ionizing irradiation did not lead to appearance of the unusual cytogenetic damages. In these conditions the speeding of the cell proliferation in different vole’s species was marked and also the increase of the frequency of those cytogenetic anomalies, which had species-specific particularities in investigated vole’s species.



Figure 1 Cytogenetic anomalies in different vole’s species


Microtus arvalis, aneuploidy,

47 chromosomes

Clethrionomys glareolus, interchromosome fusion on the type of Robertsonian translocation


Microtus oeconomus, chromatide break with deletion of fragment

Microtus agrestis



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