US EPA

8779273 

Journal Article 

Impact of Local High Doses of Radiation by Neutron Activated Mn Dioxide Powder in Rat Lungs: Protracted Pathologic Damage Initiated by Internal Exposure 

Shichijo, K; Takatsuji, T; Abishev, Z; Uzbekov, D; Chaizhunusova, N; Shabdarbaeva, D; Niino, D; Kurisu, M; Takahashi, Y; Stepanenko, V; Azhimkhanov, A; Hoshi, M 

2020 

8 

6 

171 

English 

32586004 

10.3390/biomedicines8060171 

WOS:000551233000019 

Internal radiation exposure from neutron-induced radioisotopes environmentally activated following atomic bombing or nuclear accidents should be considered for a complete picture of pathologic effects on survivors. Inhaled hot particles expose neighboring tissues to locally ultra-high doses of beta-rays and can cause pathologic damage. (MnO2)-Mn-55 powder was activated by a nuclear reactor to make (MnO2)-Mn-56 which emits beta-rays. Internal exposures were compared with external gamma-rays. Male Wistar rats were administered activated powder by inhalation. Lung samples were observed by histological staining at six hours, three days, 14 days, two months, six months and eight months after the exposure. Synchrotron radiation-X-ray fluorescence-X-ray absorption near-edge structure (SR-XRF-XANES) was utilized for the chemical analysis of the activated Mn-56 embedded in lung tissues. Mn-56 beta energy spectrum around the particles was calculated to assess the local dose rate and accumulated dose. Hot particles located in the bronchiole and in damaged alveolar tissue were identified as accumulations of Mn and iron. Histological changes showed evidence of emphysema, hemorrhage and severe inflammation from six hours through eight months. Apoptosis was observed in the bronchiole epithelium. Our study shows early event damage from the locally ultra-high internal dose leads to pathogenesis. The trigger of emphysema and hemorrhage was likely early event damage to blood vessels integral to alveolar walls. 

internal radiation exposure; Mn-56; micro-dosimetry; lung; A-bombing; elemental imaging; apoptosis; elastin; SR-XRF; X-ray absorption near-edge structure (XANES); GOLD NANOPARTICLES; MECHANISMS; PATHOGENESIS; MORBIDITY; APOPTOSIS; DISEASE; URANIUM; INJURY