Effect of Gamma Radiation on Cytogenetic and Growth Endpoints of Allium cepa Seedlings in Long-Term Experiments.

The effect of γ-radiation on the growth and cytogenetic endpoints of Allium cepa L. seedlings in a long period after irradiation in absorbed doses from 1.0 to 10.7 Gy were examined. The chromosome aberration rate was most sensitive to the radiation: it increased immediately after exposure at all doses. In the recovery period (up to 216 h) after irradiation, the chromosome aberration frequency naturally decreased but at the end of experiment in maximum doses remained above the control values. The impact of the initial level of chromosome aberrations on the inhibition of onion roots growth in the long terms after irradiation is discussed.

Effects of Gamma-Radiation on DNA Damage in Onion (Allium cepa L.) Seedlings.

The effect of γ-radiation on the level of nuclear DNA damage in onion seedlings (Allium-test) was studied using the comet assay. DNA breaks were first found in cells of onion seedlings exposed to low-dose radiation (≤ 0.1 Gy). Dose dependence of DNA damage parameters showed nonlinear behavior: a linear section in the low-dose region (below 0.1 Gy) and a dose-independent plateau in the dose range between 1 and 5 Gy. Thus, the comet assay can be used to estimate the biological effects of low-dose γ-radiation on Allium cepa seedlings.

Cytogenetic Effects of γ-Radiation in Onion (Allium cepa L.) Seedlings.

The effect of γ-radiation on the cytogenetic parameters of root meristem cells of onion seedlings was studied in laboratory experiments (Allium-test). An increase in the overall frequency of chromosomal aberrations and micronucleus frequencies in seedling cells at low γ-radiation doses (≤0.1 Gy) was detected for the first time. At a maximum absorbed dose of 13 Gy, chromosomal aberrations were detected in the majority of cells in the anaphase and telophase stages of the cell cycle, and the number of cells with multiple aberrations increased. The main contribution to the overall frequency of chromosomal aberrations, in addition to multiple aberrations, is made by the bridge-type aberrations, fragments, and lagging chromosomes. The data obtained allow using the cytogenetic indices of Allium cepa seedlings to assess the biological effects of lowdose γ-radiation.

New data on the effect of ionizing radiation on the growth of the aquatic plant Elodea canadensis in the laboratory.

Toxicological experiments with radioactive bottom sediments and extrinsic γ-irradiation have demonstrated that the growth of common elodea roots is suppressed by irradiation at doses several times lower than the established threshold dose. The effect of γ-irradiation on the growth of elodea stems has not been observed at any dose used. The data obtained show that elodea could be recommended for use as an indicator of biological effects of radiation in the range of low radiation doses.

The first results of using the Allium test in estimating the chemical and radiation toxicity of bottom sediments in the Yenisei River.

The first results of the use of the Allium test for estimation of toxicity of bottom sediments in the Yenisei River and the effect of external γ-radiation under laboratory conditions are presented. The effect of stimulation of the onion root growth, i.e., the absence of toxicity was discovered in toxicological experiments using bottom sediments and under external γ-radiation. The stimulating effect of radiation on the growth of onion roots limits the use of the Allium test for testing samples from the Yenisei River ecosystem in the zone subjected to the impact of radioactive discharges from the Mining and Chemical Combine.

Genotoxicity assessment of low-level doses of gamma radiation with the SOS chromotest and the Ames test.

This is the first study to present data on the genotoxicity of low γ-irradiation doses for E. coli and S. typhimurium cells obtained using the SOS chromotest and the Ames test. The most pronounced effect was recorded in the first 24 h of γ-irradiation. After 72 h in the Ames test and after 96 h in the SOS chromotest, a significant effect of γ-irradiation on bacterial cells was detected. The absence of genotoxicity at the later stages can be explained by the adaptation of bacterial cells to the conditions of exposure. The findings allow the bacterial test system to be used for studying the effects of low doses at the early stages of exposure to radiation.

Age-dependent accumulation of (137)Cs by pike Esox lucius in the Yenisei River.

Age-dependent accumulation of (137)Cs in the muscles and bodies of the pike Esox lucius (aged two to seven years) inhabiting a section of the Yenisei River polluted with artificial radionuclides has been studied. The content of (137)Cs in muscles varied from 0.5 to 7.0 Bq/kg of fresh weight. The maximum content of the radionuclide has been found in juveniles. The content of (137)Cs in pike muscles and body decreased considerably with age. The high content of (137)Cs in the muscles of juveniles is probably a consequence of their higher intensity of feeding as compared to older individuals, which is due to the intense growth of juveniles.

Accumulation of (241)Am by suspended matter, diatoms and aquatic weeds of the Yenisei River.

In this work we experimentally estimated the capacities of the key components of the Yenisei River (Russia): particulate suspended matter (seston), diatom microalgae, and submerged macrophytes for accumulating (241)Am from water. In our experiments large particles of seston (>8mum), comparable in size with diatoms, took up most of americium from water. The accumulation of americium by isolated diatom algae (Asterionella formosa and Diatoma vulgare) was lower than by total seston. The concentration factors (CFs) of (241)Am for seston of the Yenisei River in our experiments were (2.8-6.9).10(5); for diatoms - (1.5-4.2).10(4). The CFs for aquatic plant Elodea canadensis were within the same order of magnitude as those for diatoms. Activity concentration and CFs of (241)Am were nearly the same in experiments under dark and light conditions. This is indicative of an energy independent mechanism of americium uptake from the water by diatoms and submerged macrophytes.

Tritium in surface waters of the Yenisei River basin.

This paper reports an investigation of the tritium content in the surface waters of the Yenisei River basin near the Mining and Chemical Combine (MCC). In 2001 the maximum tritium concentration in the Yenisei River did not exceed 4 +/- 1 Bq l(-1), which is consistent with the data of 1998-99. However, it has been found that there are surface waters containing enhanced tritium as compared with the background values for the Yenisei River. For instance, in the Ploskii Stream and the Shumikha River the maximum tritium concentrations amount to 168 and 81 Bq l(-1), respectively. The source of tritium in these surface waters is the last operating reactor at the MCC, which still uses the Yenisei water as coolant. In water and sediment samples of the Bolshaya Tel River (a tributary of the Yenisei River) the tritium content turned out to be at least 10 times higher than the background values for the Yenisei River. The measurements conducted at the RPA RADON (Moscow) revealed not only tritium but also the artificial radionuclide (14)C in the Bolshaya Tel samples. The data obtained suggest that the Bolshaya Tel River receives the major part of tritium from sediments rather than from the water catchment area. This allows the conclusion that there is water exchange between the surface waters and the radioactively contaminated underground horizons of the "Severny" testing site.