Measurement of [226]Ra, [228]Ra, [137]Cs and [40]K in edible parts of two types of leafy vegetables cultivated in Tehran province-Iran and resultant annual ingestion radiation dose

The sources of radioactivity in the environment have natural, terrestrial and extraterrestrial, and anthropogenic origins. Plants may get radioactive nuclides in two ways: [i] by the deposition of radioactive fallout, [ii] by absorption from the soil. The concentrations of the natural radionuclides [[226]Ra, [228]Ra, [40]K] and the artificial radionuclide [[137]Cs] in leek and parsley in Tehran province-Iran were determined using HPGe. Also the effective dose due to the ingestion of such vegetables by the population of Tehran province was studied. The average value of radionuclide concentrations in parsley samples were measured 177.69 +/- 12.47 mBq kg[-1] fresh for [226]Ra; 349.62 +/- 28.42 mBq kg[-1] fresh for [228]Ra; 187364.6 mBq kg[-1] fresh for [40]K. The average value of radionuclide concentrations in leek samples were measured 94.31 +/- 6.46 mBq kg[-1] fresh for [226]Ra; 207.47 +/- 19.46 mBq kg[-1] fresh for [228]Ra; 174555 +/- 1704.21 mBq kg[-1] fresh for [40]K. The concentrations of [137]Cs in most of Parsley and Leek samples were below the minimum detectable activity [MDA]. The Average [226]Ra and [228]Ra activities in 29 leek and parsley samples were about 2.63 and 6.78 times the reference values, respectively. The annual effective dose resulting from the studied radionuclides for the adult population in Tehran province were found to be safe in comparison with normal background areas

The G2 checkpoint activated by DNA damage does not prevent genome instability in plant cells

Root growth, G2 length, and the frequency of aberrant mitoses and apoptotic nuclei were recorded after a single X-ray irradiation, ranging from 2.5 to 40 Gy, in Allium cepa L. root meristematic cells. After 72 h of recovery, root growth was reduced in a dose-dependent manner from 10 to 40 Gy, but not at 2.5 or 5 Gy doses. Flow cytometry plus TUNEL (TdT-mediated dUTP nick end labeling) showed that activation of apoptosis occurred only after 20 and 40 Gy of X-rays. Nevertheless, irrespective of the radiation dose, conventional flow cytometry showed that cells accumulated in G2 (4C DNA content). Simultaneously, the mitotic index fell, though a mitotic wave appeared later. Cell accumulation in G2 was transient and partially reversed by caffeine, thus it was checkpoint-dependent. Strikingly, the additional G2 time provided by this checkpoint was never long enough to complete DNA repair. Then, in all cases, some G2 cells with still-unrepaired DNA underwent checkpoint adaptation, i.e., they entered into the late mitotic wave with chromatid breaks. These cells and those produced by the breakage of chromosomal bridges in anaphase will reach the G1 of the next cell cycle unrepaired, ensuring the appearance of genome instability.