During radiotherapy, ionizing irradiation interacts with biological systems to produce free radicals, which attack various cellular components. The hematopoietic system is easily recognized to be radiosensitive and its damage may be severe. Melanin nanoparticles (MNPs) act as free radical scavengers prepared by polymerization of dopamine. In this study, a total of 110 male BALB/C mice were divided into five equal groups. Each group contained 22 mice. Mice of group A did not receive MNPs or irradiation (control group), group B was injected intraperitoneally (i.p.) with 50 mg/kg MNPs. Mice of group C and D were exposed to a dose of 7 Gy ɣ-irradiation and injected with the same dose of MNPs as in group B either 30 min pre- or post-irradiation, and group E was exposed to a dose of 7 Gy ɣ-irradiation only. The impact of MNPs on peripheral blood, spleen, and DNA damage induced by irradiation was evaluated by blood count, histopathology of the spleen, and comet assay for the DNA in the bone marrow at 1, 4, 8, and 12 days post-irradiation. Results of group E compared with control group (A) showed a significant depression in complete blood count. Additionally, histopathological observation showed the absence of megakaryocytes with delayed time post-irradiation, deposition of eosinophilic protein of their spleen appeared, as well as a remarkable decrease in spleen size was observed. Moreover, ɣ-irradiation-induced DNA damage as can be inferred from a significant increase by about 5-10 folds in all comet parameters (% of DNA, tail length, tail moment, and olive moment) in the DNA of the bone marrow. In contrast, pre-post treatment with MNPs protected hematopoietic tissues against radiation damage, and therefore, enhanced the survival of mice with 40 % in groups (C&D) compared with 10 % to group (E) till 30 days post-irradiation. In conclusion, these results demonstrated that synthetic MNPs provide significant radioprotection to the hematopoietic tissues.

No abstract

No abstract

The reaction cross section (σ R ) is calculated using the optical limit of the Glauber theory. A density-dependent effective nucleon-nucleon (NN) cross section σ NN is considered. Finite and zero range NN interactions are studied. The effect of finite range and an appropriate local density can increase σ R up to 20% compared to the zero range at constant density (0.16 fm −3 ), while a zero range calculation with free NN cross section increases σ R up to 13%. These factors affect the values of the rms radii for neutron rich nuclei extracted from σ R . PACS number(s): 24.10. Ht, 25.60.Dz, Recently, the optical limit to Glauber theory [1] has been used with considerable success to describe the nucleus-nucleus reaction cross section σ R [2]. The inputs to these calculations are the NN cross section σ NN and the density distribution of the interacting nuclei. The cross section σ R is usually calculated by assuming a zero range force of the interacting nucleons, and σ NN is considered through different approaches. First, σ NN is taken directly as a free NN cross section σ f NN without density dependence [3,4], and Cai Xiangzhou et al.[5] developed a density-dependent formula (in medium) averaged over the isospin of the interacting nucleiσ NN . In this approach, σ NN is usually evaluated at a constant global density ρ = 0.17 fm −3 [2,5].The method of calculating σ R is improved by using the density-dependent σ NN derived in Ref. [5]. One of these attempts [6] showed the effects of the in-medium NN cross section on σ R , using zero range NN force and the isospin averaged constant density-dependent NN cross section. Later, Warner et al. [7] introduced the local matter density in σ NN for each volume element of the nuclear overlap region; as a result the value of σ R is reduced by a relatively small percentage compared with that obtained using free NN cross section σ f NN . The effect of the finite range force [8] is found to increase σ R by about 5% compared to the zero range force for the reaction 238 U + 12 C.The main in-medium effect in the NN cross section at low and intermediate energies is due to Pauli blocking; this prevents the scattered nucleons from going into occupied states in binary collisions between the projectile and target nucleons. The accurate treatment of Pauli blocking is the geometric approach [9], which requires numerical calculation of a fivefold integral to get the in-medium NN cross section. Due to this complexity, many authors simplified the effect of Pauli blocking by making different approximations [7,[9][10][11].Although most of the recent calculations of σ R use the density dependence parametrization of Ref.[5] to include inmedium effects in σ NN , it is interesting to compare this method with the one obtained by the geometrical approach for Pauli blocking [9], when either finite or zero range NN interaction is assumed.In the optical limit of the Glauber theory, the calculation of σ R is known to be affected by the in-medium effects of σ NN , the finite range of the NN force, and the root ...