Radioresponse of human lymphocytes pretreated with boron and gadolinium as assessed by the comet assay

Boron and gadolinium are among the nuclides that hold a unique property of being a neutron capture therapy agent. Neutron beams have often a considerable portion of gamma rays with fast neutrons. Gamma rays, as beam contaminants, can cause considerable damage to normal tissues even if such tissues do contain high boron concentrations. The modification of radioresponse in human lymphocytes pretreated with boron or gadolinium compound was studied by assessing the DNA damage using single cell gel electrophoresis [SCGE], the comet assay. The lymphocytes from the human peripheral blood were irradiated with 0, 1, 2 and 4 Gy of gamma rays from a 60Co isotopic source with or without pretreatment of boron or gadolinium compound for 10 minutes at 4°C. Post-irradiation procedures included slide preparation, cell-lysing, unwinding and electrophoresis, neutralization, staining, and analytic steps, gel electrophoresis. The results indicate that pretreatment with boron compound [50 nM or 250 nM of 10B] is effective in reducing the radiosensitivity of the lymphocyte DNA. Conversely, pretreatment with gadolinium compound [50 nM] led to a dose-dependent increase in the radiosensitivity, most prominently with a dose of 4 Gy [P<0.001]. Furthermore, when the lymphocytes were pretreated with a combined mixture [1:1] of boron [250 nM] and gadolinium [50 nM] compounds, the reduced radiosensitivity was also observed

YCF and YAP gene expressions in yeast cells after irradiation combined with mercury treatment

All aerobically growing organisms suffer from exposure to oxidative stress, caused by partially reduced forms of molecular oxygen, known as reactive oxygen species [ROS]. These are highly reactive and capable of damaging cellular constituents such as DNA, lipids and proteins. Consequently, cells from many different organisms have evolved mechanisms to protect their components against ROS. It is known to have some genes for resistance to heavy metals and ionizing radiation [IR]. Saccharomyces cerevisiae is an ideal model organism for deducing biological processes in human cells. In this work, cell viability and gene expression was investigated in yeasts treated with IR, HgCl[2], and IR combined with HgCl[2]. Cell viability was measured by colony forming unit [CFU] method in an YPD medium. Gene expression was analyzed by the Real-time PCR. The viability was lower at the higher dose. At a dose above a certain level, the viability came down to zero. The combined treatment decreased the viability, as well. Metal resistance genes were expressed in the cells treated with HgCl[2]. In a similar way, irradiation also triggered the expression of some radiation resistance genes. YCF and YAP genes were induced consecutively with the HgCl[2] concentration, and also with a higher total dose under a lower dose rate condition. These two genes were, however, expressed differently under the 0.2 mM HgCl[2] treatment condition. In the cells treated with 0.1-o.2 mM HgCl[2], the viability was higher than with any other concentrations. The results demonstrated that the higher dose induced more expression of oxidative stress resistance genes related to cell survival mechanism. Combined treatment of radiation with mercury chloride resulted in synergistic effects leading to a higher expression of the genes than treatment of a single stressor alone