The neuromorphological correlates of prolonged radiation exposure

Abstract

Relevance.Liquidators of the consequences of radiation accidents have an increase in neuropsychiatric diseases. However, the structural and functional rearrangement of brain neurons under prolonged low radiation exposure remains virtually unexplored, which makes it difficult to assess the pathogenesis of these diseases.Intention.To study morphological correlates of prolonged low radiation effects on brain neurons in the model of radiobiological experiment.Method.270 white outbred male rats aged 4 months were exposed to radiation-quanta of 60Co in equal portions in total doses of 10; 20; 50 and 100 cGy with a dose rate of 0.5 Gy/h over 5 days. Age control consisted of animals exposed to false radiation. Animal studies complied with GLP standards. Brain fragments were taken after 1 day, 6, 12, 18 and 24 months after irradiation. After a standard histological treatment, changes in the tinctorial properties of neurons, their morphometric parameters, total protein and nucleic acids were evaluated.Results and their analysis. At the end of the observation period, the number of normochromic neurons decreased and the number of hyper and hypochromic cells increased, as well as their destructive forms. The neuro-cellular index decreased over time suggesting the death of some neurons, but without a statistically significant decrease in their number per area. In the post-irradiation period there were observed phase changes in the size of the cytoplasm, nucleus and nucleolus of neurons, as well as the content of protein and nucleic acids (RNA in the cytoplasm and nucleoli, DNA in the nuclei), more pronounced in irradiated animals and sometimes different from those observed in age control animals. As a result, a number of neuromorphological parameters in some periods of observation were not consistent with those in control animals, with a certain instability in the structural and functional organization of neurons.Conclusion.Prolonged low-dose ionizing radiation does not cause significant organic changes in the brain. However, increased radiation exposure or other concomitant adverse factors can be associated with further instability of the structural and functional organization of neurons and serve as a material substrate for a number of deviations in the central nervous system.