An examination of blind mole-rat (Nannospalax xanthodon) brain, cerebellum, and spinal cord tissues: A histological and stereological study

Abstract

The purpose of this study was to perform a histological examination of blind mole-rat (Nannospalax xanthodon) brain, cerebellum, and spinal cord tissues. Six blind mole-rats were caught in a natural environment, anesthetized with ether, and sacrificed. Brain, cerebellum, and spinal cord tissues were then removed. All tissues were kept in 10% formaldehyde for one week, at the end of which they were subjected to routine histological procedures and embedded in blocks. Five micron-thick sections were taken from the blocks (5 and 15 micron thick from spinal cord tissues). All sections were then stained with hematoxylin-eosin, Cresyl Violet, and DAPI. These sections were then evaluated under light and fluorescent microscopes. The blind mole-rats weighed 201.3 ± 61 g, the brains and cerebella weighed 1.8 ± 0.3 mg and 0.32 ± 0.05 mg, respectively, and the brain, cerebellum, and spinal cord volumes were 1.49±0.46 ml, 0.33± 0.08 ml, and 2.53± 0.19 µm3, respectively. No histological variation was observed in the brain or cerebellum tissues. However, examination of the spinal cord tissue revealed differences compared to humans and other rodents. The spinal cord exhibited a segmented, lobulated appearance, each lobe itself exhibiting the characteristics of a small spinal cord. No butterfly appearance was observed, and white and gray matter transitions were irregular, with less white and more gray matter. The location of the anterior and posterior horns was unclear. The motor neuron cells were also small in size. No significant variations were observed at nuclear organization (DAPI signals) between any tissues. In conclusion, the blind mole-rats were normal in weight, increased brain and cerebellum tissue weight and volumes were observed, while a decrease was determined in spinal cord tissue volumes. The brain and cerebellum were normal at histological examination, while structural differences were detected in the spinal cord.

Keywords

• Brain
• Cerebellum
• Spinal Cord
• Nanosplax xanthodon
• Stereology
• Blind mole-rat

References

1. Altwasser, R., Paz, A., Korol, A., Manov, I., Avivi, A., Shams, I. (2019). The transcriptome landscape of the carcinogenic treatment response in the blind mole rat: insights into cancer resistance mechanisms. BMC Genomics, 8, 20-17. https://doi.org/10.1186/s12864-018-5417-z.
2. Aktürk, Z., Odacı, E., İkinci, A., Baş, O., Canpolat, S., Çolakoğlu, S., Sönmez, O.F. (2014). Effect of Ginkgo biloba on brain volume after carotid artery occlusion in rats: a stereological and histopathological study. Turk J Med Sci, 44, 546-53. https://doi.org/10.3906/sag-1305-40.
3. Aydın, A. ve Karan, M. (2012). The spinal nerves forming the brachial plexus in mole-rats (Spalax leucodon), Veterinarni Medicina, 57, 430–433.
4. Avivi, A., Resnick, M.B., Nevo, E., Joel, A., Levy, A.P. (1999). Adaptive hypoxic tolerance in the subterranean mole rat Spalax ehrenbergi: the role of vascular endothelial growth factor. FEBS Lett, 452, 133–140. https://doi.org/10.1016/S0014-5793(99)00584-0.
5. Avivi, A., Shams, I., Joel, A., Lache, O., Levy, A.P., Nevo, E. (2005). Increased blood vessel density provides the mole rat physiological tolerance to its hypoxic subterranean habitat. Federation of American Societies for Experimental Biology (FASEB J), 19(10), 1314-6. https://doi.org/10.1096/fj.04-3414fje.
6. Cernuda-Cernuda, R., DeGrip, W.J., Cooper, H.M., Nevo, E., García-Fernández, J.M. (2005). The retina of Spalax ehrenbergi: novel histologic features supportive of a modified photosensory role. Invest Ophthalmol Vis Sci, 43, 2374- 83.
7. Frahm, H.D., Rehkämper, G., Nevo, E. (1997). Brain structure volumes in the mole rat, Spalax ehrenbergi (Spalacidae, Rodentia) in comparison to the rat and subterrestrial insectivores. J Hirnforsch, 38, 209-22.
8. Fang, Y., Che, X., You, M., Xu, Y., Wang, Y. (2020). Perinatal exposure to nonylphenol promotes proliferation of granule cell precursors in offspring cerebellum: Involvement of the activation of Notch2 signaling. Neurochem Int, 140,104843. https://doi.org/10.1016/j.neuint.2020.104843.

9. Hadid, Y., Németh, A., Snir, S., Pavlíček, T., Csorba, G., Kázmér, M., Major, A., Mezhzherin, S., Rusin, M., Coşkun, Y., Nevo, E. (2012). Is evolution of blind mole rats determined by climate oscillations? PLoS One, 7(1):e30043.
10. Keleş, A.İ. (2019). Sağlık alanında kullanılan kantitatif yöntem, Stereoloji. Dicle Tıp Dergisi / Dicle Med J, 46, 615- 621. https://doi.org /10.5798/dicletip.536434.
11. Keleş, A.İ., Nyengaard, J.R., Odacı, E. (2019). Changes in pyramidal and granular neuron numbers in the rat hippocampus 7 days after exposure to a continuous 900-MHz electromagnetic field during early and mid-adolescence. J Chem Neuroanat, 26,101-101681. https://doi.org/10.1016/j.jchemneu.2019.101681.
12. Keleş, A.İ., Süt, B.B., Kankiliç, T. (2020). Histopathological analysis of the eye and optic nerve structure in the blind mole rat. Dicle Med J 47 (3): 638-644. . https://doi.org /10.5798/dicletip.800025.
13. Keleş, A.İ., Süt, B.B. (2021). Histopathological and epigenetic alterations in the spinal cord due to prenatal electromagnetic field exposure: an H3K27me3-related mechanism. Toxicology and Industrial Health, 37(4), 189-197. https://doi.org//10.1177/0748233721996947.
14. Kardong, K.V. (1995). “Vertebrates’’, Comparative Anatomy, Function, Evolution, Dubuque, Melbourne, Oxford, Wm. C. Brown Publishers (Times Mirror International Publishers), 17, 777.
15. Manov, I., Hirsh M., Lancu T.C., Malik A., Sotnichenko N., Band M., Avivi A., Shams I. (2013). Pronounced cancer resistance in a subterranean rodent, the blind mole-rat, Spalax: in vivo and in vitro evidence. BMC biology, 9, 11-91.
16. Nordmann, A. (1840). Observations sur la faune pontique. A. Demidoff Voyage dans la Russie Meridion, 3(35). Nevo, E., Filippucci, M.G., Redi, C., Simson, S., Heth, G., Beiles, A. (1995). Karyotypeandgeneticevolution in speciation of subterraneanmolerats of thegenusSpalax in Turkey. BiologicalJournal of theLinneanSociety, 54, 203-29. https://doi.org/10.1111/j.1095-8312.1995.tb01034.x.
17. Sözen, M. (2005). A biological investigation on Turkish Spalax Guldenstaedt, 1770 (Mammalia: Rodentia). G.Ü. Fen Bilimleri Dergisi, 18(2), 167-181.
18. Tian, X., Azpurua, J., Hine, C., Vaidya, A., Myakishev-Rempel, M.,Ablaeva, J., Mao, Z., Nevo, E.,Gorbunova, V., Seluanov, A. (2013). High-molecular-mass hyaluronan mediates the cancer resistance of the naked mole rat. Nature, 499, 346-349. https://doi.org/10.1038/nature12234.