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. 2017 Mar;56(1):55-61.
doi: 10.1007/s00411-016-0676-z. Epub 2017 Feb 8.

Internal exposure to neutron-activated 56Mn dioxide powder in Wistar rats-Part 2: pathological effects

Kazuko Shichijo  1 , Nariaki Fujimoto  2 , Darkhan Uzbekov  3 , Ynkar Kairkhanova  3 , Aisulu Saimova  3 , Nailya Chaizhunusova  3 , Nurlan Sayakenov  3 , Dariya Shabdarbaeva  3 , Nurlan Aukenov  3 , Almas Azimkhanov  4 , Alexander Kolbayenkov  4 , Zhanna Mussazhanova  1 , Daisuke Niino  1 , Masahiro Nakashima  1 , Kassym Zhumadilov  5 , Valeriy Stepanenko  6 , Masao Tomonaga  1 , Tolebay Rakhypbekov  3 , Masaharu Hoshi  7
Affiliations

Internal exposure to neutron-activated 56Mn dioxide powder in Wistar rats-Part 2: pathological effects

Kazuko Shichijo et al. Radiat Environ Biophys. 2017 Mar.

Erratum in

Abstract

To fully understand the radiation effects of the atomic bombing of Hiroshima and Nagasaki among the survivors, radiation from neutron-induced radioisotopes in soil and other materials should be considered in addition to the initial radiation directly received from the bombs. This might be important for evaluating the radiation risks to the people who moved to these cities soon after the detonations and probably inhaled activated radioactive "dust." Manganese-56 is known to be one of the dominant radioisotopes produced in soil by neutrons. Due to its short physical half-life, 56Mn emits residual radiation during the first hours after explosion. Hence, the biological effects of internal exposure of Wistar rats to 56Mn were investigated in the present study. MnO2 powder was activated by a neutron beam to produce radioactive 56Mn. Rats were divided into four groups: those exposed to 56Mn, to non-radioactive Mn, to 60Co γ rays (2 Gy, whole body), and those not exposed to any additional radiation (control). On days 3, 14, and 60 after exposure, the animals were killed and major organs were dissected and subjected to histopathological analysis. As described in more detail by an accompanying publication, the highest internal radiation dose was observed in the digestive system of the rats, followed by the lungs. It was found that the number of mitotic cells increased in the small intestine on day 3 after 56Mn and 60Co exposure, and this change persisted only in 56Mn-exposed animals. Lung tissue was severely damaged only by exposure to 56Mn, despite a rather low radiation dose (less than 0.1 Gy). These data suggest that internal exposure to 56Mn has a significant biological impact on the lungs and small intestine.

Keywords: A-bombing; Internal radiation exposure; Lung; Manganese-56; Rats.

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Conflict of interest statement

Funding

This work was supported by Semey State Medical University, Kazakhstan, and Grant-in-Aids (#26257501 and #23510064) from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

Conflict of interest

Author Kazuko Shichijo declares that she has no conflict of interest; Author Nariaki Fujimoto declares that he has no conflict of interest; Author Darkhan Uzbekov declares that he has no conflict of interest; Author Ynkar Kairkhanova declares that she has no conflict of interest; Author Aisulu Saimova declares that she has no conflict of interest; Author Nailya Chaizhunusova declares that she has no conflict of interest; Author Nurlan Sayakenov declares that he has no conflict of interest; Author Dariya Shabdarbaeva declares that she has no conflict of interest; Author Nurlan Aukenov declares that he has no conflict of interest; Author Almas Azimkhanov declares that he has no conflict of interest; Author Alexander Kolbayenkov declares that he has no conflict of interest; Author Zhanna Mussazhanova declares that she has no conflict of interest; Author Daisuke Niino declares that he has no conflict of interest; Author Masahiro Nakashima declares that he has no conflict of interest; Author Kassym Zhumadilov declares that he has no conflict of interest; Author Valeriy Stepanenko declares that he has no conflict of interest; Author Masao Tomonaga declares that he has no conflict of interest; Author Tolebay Rakhypbekov declares that he has no conflict of interest; Author Masaharu Hoshi declares that he has no conflict of interest.

Ethical approval

All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. The animal experiment was approved by the Animal Experiment Committee of Semey Medical University, Republic of Kazakhstan, and conducted in accordance with the Institutional Guide for Animal Care and Use.

Figures

Fig. 1
Fig. 1
Small intestine of rats 60 days after exposure. A number of mitotic cells (arrows) per crypt were noted in the 56Mn group (a); the number in the 60Co group (b) was similar to that in the control group. HE staining, original magnification 100×
Fig. 2
Fig. 2
Lung of rats 3 days after exposure. Severe emphysema (a), and hemorrhage (a1) were observed in the 56Mn group. No pathological changes were observed in the Mn group (b). Control group (c). HE staining, original magnification ×10
See this image and copyright information in PMC

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