Ismail Bahari

Micronucleated erythrocytes as an assay to assess actions by physical and chemical genotoxic agents in Clarias gariepinus

An in vivo study on the effects of both physical (gamma-radiation) and chemical (mitomycin C) genotoxic agents was carried out with the catfish species, Clarias gariepinus. The fish were either exposed to gamma-radiation at doses of 0-9 Gy or injected intraperitoneally with mitomycin C at concentrations of 0-2 mg/kg. Micronucleated erythrocytes were sampled from 0 to 60 days post treatment. Data obtained showed a time-dependent response of the induction of micronucleated erythrocytes with both genotoxic agents. A linear dose-dependent increase was observed 2-4 days after treatment. These data show the importance of sampling time in the micronucleus assay with Clarias gariepinus.

Investigation of the dependence of inactivation coefficient on pertinent physical quality parameters to low doses ionizing radiation.

Inactivation constant for V79 cells has been extracted from radiobiology experiments that utilize charged particles to irradiate mammal cells in vitro. Physical parameters such as effective charge, radiation mean free path and linear ionization which characterized protons and heluim-4 particles are determined using of standard values. The relationship between inactivation constant α and physical quality parameters have been determined, in this research, for protons and heluim-4 particles. This approach allows getting the characteristic biological response of inactivation of V79 cells in terms of each selected physical quality parameter. The best regression models are formulated for each obtained relationship.

Physical Parameters that Influence the Effectiveness of Ionizing Radiation at Low Doses

Relative biological effectiveness (RBE) for the inactivation of V79 cells were determined using the initial slopes of survival curves (published in literature), the physical quality parameters are interpolated utilizing the standard values relevant to charged particles such as protons and heliums. The issues of utilizing physical parameters as quantifier of radiation effects that influence the effectiveness have been investigated. The results show that the effectiveness may represent in terms of other physical parameters rather than linear energy transfer (LET). Meanwhile, mean free path for linear primary ionization (λ) is expressed the generalized specifier physical quality parameter to quantify ionizing radiation effects at lower doses. Therefore, plot of mean free path as a function of RBE has been made to identify the physical features of this parameter as an alternative physical quality for LET.

Alternative Physical Quality Parameters Influences Effectiveness of Lower Doses Ionizing Radiation

It has been proved in many studied that the absorbed dose is not good physical quality parameter to quantify the radiation effects at lower doses. However relative biological effect (RBE) is still used as a major parameter of radiation effectiveness. Whereas linear energy transfer (LET) is inadequate physical parameter, therefore the weaknesses in using RBE‐LET system for radiation protection have been investigated. Secondary data of V79 has reanalyzed to help complement the inadequacy current method in assessing cell inactivation at lower doses. Results of analysis show that the effectiveness of densely ionizing radiation is better quantified using mean free path (λ).