The neuromorphological correlates of prolonged radiation exposure

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.

1. Azizova T.V., Gus’kova A.K., Sulina M.V. Nevrologicheskie sindromy pri professional’nom khronicheskomvozdeistvii ioniziruyushchego izlucheniya (blizhaishie effekty) [Neurological syndromes from occupational chronic radiation exposure (the early effects)]. Meditsinskaya radiologiya i radiatsionnaya bezopasnost’ [Medical radiology and radiation safety]. 2002. Vol. 47, N 6. Pp. 36–45. (In Russ.)

2. Aleksanin S.S. Patogeneticheskie zakonomernosti formirovaniya somaticheskoi patologii posle radiatsionnykh avarii v otdalennom periode [Pathogenetic regularities of somatic pathology formation after radiation accidents in the remote period]. Vestnik Rossiiskoi voenno-meditsinskoi akademii [Bulletin of Russian Military Medical Academy]. 2008. N 3. Application. Pp. 10–13. (In Russ.)

3. Gundarova O.P., Fedorov V.P., Afanas’ev R.V., Zuev V.G. Otsenka psikhonevrologicheskogo statusa likvidatorov radiatsionnykh avarii [Assessment of neuropsychiatric status of the liquidators of radiation accidents]. Voronezh. 2012. 232 p. (In Russ.)

4. Gus’kova A.K. Radiatsiya i mozg cheloveka [Radiation and the human brain]. Meditsinskaya radiologiya i radiatsionnaya bezopasnost’ [Medical radiology and radiation safety]. 2001. Vol. 46, N 5. Pp. 47–55. (In Russ.)

5. Legeza V.I., Reznik V.M., Pimburskii V.F. K voprosu ob osobennostyakh mnogoletnei dinamiki urovnei boleznei sistemy krovoobrashcheniya u voennosluzhashchikh – likvidatorov posledstvii avarii na Chernobyl’skoi AES [About cardiovascular disease rates over years in military liquidators of Chernobyl aftermath] Mediko-biologicheskie i sotsial’no-psikhologicheskie problemy bezopasnosti v chrezvychainykh situatsiyakh [Medico-Biological and Socio-Psychological Problems of Safety in Emergency Situations]. 2016. N 1. Pp. 34–40. (In Russ.)

6. Nikiforov A.M., Aleksanin S.S., Chugunova L.N. Osobennosti psikhologicheskogo statusa i mediko-psikhologicheskaya reabilitatsiya uchastnikov avariino-vosstanovitel’nykh rabot na ChAES [Medical-psychological rehabilitation of clean-up workers of Chernobyl aftermath]. Meditsinskaya radiologiya i radiatsionnaya bezopasnost’ [Medical radiology and radiation safety]. 2002. Vol. 47, N 5. Pp. 43–50. (In Russ.)

7. Rossiiskii Natsional’nyi doklad 25 let Chernobyl’skoi avarii: itogi i perspektivy preodoleniya ee posledstvii v Rossii. 1986– 2011 [The Russian national report: 25 years after the Chernobyl accident: results and prospects of overcoming its consequences in Russia. 1986–2011] / Eds.: S.K. Shoigu, L.A. Bol’shov. Moskva. 2011. 160 p. (In Russ.)

8. Rumyantseva G.M., Chinkina O.V., Levina T.M. Psikhicheskaya dezadaptatsiya uchastnikov likvidatsii avarii na Chernobyl’skoi AES [Mental disadaptation of participants of liquidation of the Chernobyl accident]. Russkii meditsinskii zhurnal [Russian Medical Journal]. 1998. N 1. Pp. 23–28. (In Russ.)

9. Torubarov F.S., Bushmanov A.Yu. Nevrologicheskie aspekty ostrykh radiatsionnykh porazhenii [Neurological aspects of acute radiation injuries]. Meditsinskaya radiologiya i radiatsionnaya bezopasnost’ [Medical radiology and radiation safety]. 1999. Vol. 44, N 6. Pp. 64–70. (In Russ.)

10. Torubarov F. S., Zvereva Z. F. Nevrologicheskie aspekty ostroi luchevoi bolezni cheloveka (klinicheskie nablyudeniya) [Neurological aspects of acute radiation sickness in humans (clinical observations)]. Moskva. 2009. 208 p. (In Russ.)

11. Ushakov I.B., Arlashchenko N.I., Soldatov S.K., Popov V.I. Ekologiya cheloveka posle Chernobyl’skoi katastrofy: radiatsionnyi ekologicheskii stress i zdorov’e cheloveka [Human ecology after the Chernobyl accident: radiation, environmental stress and human health]. Moskva.: Voronezh. 2001. 723 p. (In Russ.)

12. Ushakov I.B., Fedorov V.P., Saurina O.S., Zuev V.G. Radiatsionnye morfofunktsional’nye effekty mozga [Radiation morphofunctional effects of the brain]. Voronezh. 2010. 287 p. (In Russ.)

13. Ushakov I.B., Fedorov V.P. Malye radiatsionnye vozdeistviya i mozg [Low-dose radiation exposure and brain]. Voronezh. 2015. 536 p. (In Russ.)

14. Ushakov I.B., Fedorov V.P., Gundarova O.P. [et al.]. Neiromorfologicheskie korrelyaty malykh radiatsionnykh vozdeistvii [Neuromorphological correlates of low-dose radiation effects]. Mediko-biologicheskie i sotsial’no-psikhologicheskie problemy bezopasnosti v chrezvychainykh situatsiyakh [Medico-Biological and Socio-Psychological Problems of Safety in Emergency Situations]. 2016. N 1. Pp. 71–78. (In Russ.)

15. Ushakov I.B., Fedorov V.P. Vozdeistvie faktorov Chernobyl’skoi avarii na psikhonevrologicheskii status likvidatorov-vertoletchikov [The impact of the Chernobyl accident factors on the psychoneurological status of helicopter pilots-liquidators]. Meditsinskaya radiologiya i radiatsionnaya bezopasnost’ [Medical radiology and radiation safety]. 2018. Vol. 63. N 4. Pp. 22– 32. (In Russ.)

16. Fedorov V. P., Gundarova O. P., Sgibneva N. V., Maslov N. V. Radiatsionno-indutsirovannye i vozrastnye izmeneniya neironov mozzhechka [Radiation-Induced and Age-Related Changes in Cerebellar Neurons]. Meditsinskaya radiologiya i radiatsionnaya bezopasnost’ [Medical radiology and radiation safety]. 2015. Vol. 60, N 4. Pp. 12–18. (In Russ.)

17. Fedorov V.P., Ushakov I.B., Fedorov N.V. Tserebral’nye effekty u likvidatorov Chernobyl’skoi avarii [Cerebral effects in liquidators of the Chernobyl accident]. Saarbrьcken: LAP LAMBERT Academic Publishing, 2016. 390 p. (In Russ.)

18. Shamrej V.K., Chistyakova E.I., Matyshchina E.N. [et al.]. Radiatsionnaya psikhosomaticheskaya bolezn’ u likvidatorov posledstvii avarii na Chernobyl’skoi AES [Radiation psychosomatic illness in liquidators of Chernobyl NPP disaster]. Mediko-biologicheskie i sotsial’no-psikhologicheskie problemy bezopasnosti v chrezvychainykh situatsiyakh [Medico-Biological and Socio-Psychological Problems of Safety in Emergency Situations]. 2016. N 1. Pp. 21–33. (In Russ.)