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The boundaries of human space exploration continue to expand with new technology and discoveries making it even more important to investigate the effects of space on biological systems. Although humans have explored space in small increments, reproductive studies must be conducted to determine if stable short- or long-term residences for humans can exist in space. This study explored the effects of whole-body proton radiation on uterine smooth muscle known as the myometrium. Two types of mice utilized in this study were C57BL/6 and B6.129S6Cybbtm1Din/J NOX2 knockout mice. C57BL/6 mice are standard laboratory mice that were used to represent the wildtype treatment group (N=18). The B6.129S6Cybbtm1Din/J NOX2 knockout mice have the NADPH Oxidase 2 gene shut off and represented the NOX2 Knockout treatment group (N=18). A third treatment group was made up of half of the C57BL/6 mice and were fed apocynin (N=18). Apocynin has been shown to inhibit NAPDH oxidase production in mice. NADPH Oxidase 2 is involved in the production of deleterious Reactive Oxygen Species (ROS); thus, apocynin should reduce the production of ROS in mice exposed to radiation. Different doses of radiation (0Gy, 0.5Gy, and 2.0Gy) were applied to the myometrium creating three different treatment subgroups within each mouse strain. The mice received 250 MeV protons at an approximate dose rate of 70cGy/ minute. Myometrium tissue was obtained one week following the radiation treatment. The uteri were removed, embedded, sectioned, and stained in hematoxylin and eosin solution. Thickness was determined by taking five measurements each of the outer longitudinal layer length, the inner circular layer length and the total length of both layers of the myometrium for three individual pieces of tissue for each animal. A one-way analysis of variance (ANOVA) was used to determine statistical differences between the groups and subgroups. Wildtype control mice exposed to 2.0Gy (N=5) of radiation had the thickest outer longitudinal layers compared to wildtype mice exposed to 0Gy (N=5) and 0.5Gy (N=6) (p=0.005, p=0). In the apocynin fed and Knockout treatment groups, the subgroups exposed to 0Gy had the thickest layers compared to their respective subgroups exposed to 0.5Gy and 2.0Gy. The apocynin fed mice exposed to 0Gy (N=6) outer longitudinal layer was statistically significantly thicker than the apocynin-fed mice exposed to 0.5Gy (p=0.004; N=6). The inner circular layer of the apocynin-fed mice exposed to 0.5Gy was statistically significantly thicker than the apocynin-fed mice exposed to 2.0Gy (p=0.001; N=6). Amongst the treatment groups, the wildtype control versus the apocynin fed mice exposed to 0Gy showed the apocynin-fed group to have the thicker outer longitudinal layer (p=0.003) and combined layers (p=0.001). Overall, the knockout group showed no statistical difference when compared to the wildtype control group. Further studies are necessary to reduce the possible confounding effect of the estrous cycle in the mice. The different phases of the mice estrus cycle may inadvertently affect the mouse uterine thickness due to the fluctuations in hormones. This study will add to the limited research regarding the female reproductive system in hopes of expanding the knowledge needed to actualize space colonization.
East Tennessee State University
Honors Thesis - Withheld
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Bulawa, Lillith, "The Effects of Total Body Proton Irradiation on Mouse Myometrium" (2020). Undergraduate Honors Theses. Paper 548. https://dc.etsu.edu/honors/548
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