Tein was subjected to SDS-PAGE, transferred to polyvinylidene difluoride, and probed with antibodies specific against the following substrates: Mouse antiAmyloid Precursor Protein (Covance, 1:1000), Rabbit anti-bCTF (Sigma, 1:1000), Rabbit anti-IDE (Calbiochem 1:1000), Rabbit anti-LRP1 (Epitomics, 1:10,000), and a-tubulin (Calbiochem, 1:5000). Only the male 0 cGy and 100 cGy samples were used for Western blots.ResultsTo assess the effect of iron galactic cosmic radiation on memory and cognition two separate tests were employed prior to tissue harvest at 9.5 mo for males and 7 mo for females. To assess hippocampal-dependent memory, the first test used was contextual fear conditioning (Fig. 1A). We found an overall significant difference in freezing behavior as measured by one-way ANOVA in the male group [F(2,32) = 5.122, p = .0118] and post-hoc analysis revealed a significant decrease in freezing behavior between the 0 cGy and 100 cGy conditions. In female mice at 7 months of age, 
there was a trend towards increased freezing after 100 cGy irradiation (p = .0561) (Fig. 1A). Radiation did not have a significant effect on freezing relative to a novel environment or a cued tone response in either sex (Fig. 1B). The second cognitive test used was a novel object recognition paradigm, which depends on multiple areas of the brain. One-way ANOVA revealed a significant change in the males [F (2,34) = 11.99, p,.0001] and post-hoc showed a decrease in exploratory time spent with the novel object for both the 10 cGy and 100 cGy irradiated male groups (Fig. 1C). A Student’s t-test showed significant loss of novel object recognition in the female group exposed to 100 cGy (p,.0001). The radiation induced defects in learning and memory prompted us to examine if there were any alterations of Ab pathology. Figure 2 shows results from two MC-LR different kinds of amyloid stains. Congo red was used to stain dense fibrillar plaques (Fig. 2A, B) and 6E10, which recognizes an epitope within amino acid residues 1?6 of Ab, labels fibrillar and non-fibrillar Ab (Fig. 2C, D). At 9.5 mo of age, exposure of male mice to 100 cGy of radiation was I-BRD9 sufficient to cause a significant increase of 38.0 in Congo red- [F(2,33) = 4.839, p = .014] (Fig. 2B) and a 53.8 increase in 6E10- [F(2,32) = 8.132, p = .0014) (Fig. 2D) labeledplaque burden 23727046 (percent area). The 7 mo-old females did not show any significant difference in Congo red (p = .1011) or 6E10 (p = .1585). Using 6E10 labeling, male mice exposed to 56Fe particle radiation also showed a significant increase of 300 6 56 to 447 6 147 (mean 6 SD, p = .0044) (Fig. 2E) in the average number of plaques after 100 cGy irradiation. Additionally, there was a trend towards larger plaque size (587 6 50 to 628 6 51 mm2, mean 6 SD, p = .052) (Fig. 2F) in the males irradiated with 100 cGy compared to controls (0 cGy). Females did not show any changes in plaque size or number with radiation. To strengthen our histology data and determine whether different forms of Ab were altered after radiation, we prepared soluble and insoluble fractions of homogenized hemibrains and used ELISAs specific for Ab peptides with C-terminals of 40 or 42 (Fig. 3). For the soluble fraction, there was a significant 35.9 increase in Ab40 levels with 100 cGy radiation in male mice compared to non-irradiated controls by one-way ANOVA [F(2,34) = 4.332 p = .0211] (Fig. 3A). Moreover, male mice showed significant 14.8 and 10.2 increases in concentrations of Ab42 in t.Tein was subjected to SDS-PAGE, transferred to polyvinylidene difluoride, and probed with antibodies specific against the following substrates: Mouse antiAmyloid Precursor Protein (Covance, 1:1000), Rabbit anti-bCTF (Sigma, 1:1000), Rabbit anti-IDE (Calbiochem 1:1000), Rabbit anti-LRP1 (Epitomics, 1:10,000), and a-tubulin (Calbiochem, 1:5000). Only the male 0 cGy and 100 cGy samples were used for Western blots.ResultsTo assess the effect of iron galactic cosmic radiation on memory and cognition two separate tests were employed prior to tissue harvest at 9.5 mo for males and 7 mo for females. To assess hippocampal-dependent memory, the first test used was contextual fear conditioning (Fig. 1A). We found an overall significant difference in freezing behavior as measured by one-way ANOVA in the male group [F(2,32) = 5.122, p = .0118] and post-hoc analysis revealed a significant decrease in freezing behavior between the 0 cGy and 100 cGy conditions. In female mice at 7 months of age, there was a trend towards increased freezing after 100 cGy irradiation (p = .0561) (Fig. 1A). Radiation did not have a significant effect on freezing relative to a novel environment or a cued tone response in either sex (Fig. 1B). The second cognitive test used was a novel object recognition paradigm, which depends on multiple areas of the brain. One-way ANOVA revealed a significant change in the males [F (2,34) = 11.99, p,.0001] and post-hoc showed a decrease in exploratory time spent with the novel object for both the 10 cGy and 100 cGy irradiated male groups (Fig. 1C). A Student’s t-test showed significant loss of novel object recognition in the female group exposed to 100 cGy (p,.0001). The radiation induced defects in learning and memory prompted us to examine if there were any alterations of Ab pathology. Figure 2 shows results from two different kinds of amyloid stains. Congo red was used to stain dense fibrillar plaques (Fig. 2A, B) and 6E10, which recognizes an epitope within amino acid residues 1?6 of Ab, labels fibrillar and non-fibrillar Ab (Fig. 2C, D). At 9.5 mo of age, exposure of male mice to 100 cGy of radiation was sufficient to cause a significant increase of 38.0 in Congo red- [F(2,33) = 4.839, p = .014] (Fig. 2B) and a 53.8 increase in 6E10- [F(2,32) = 8.132, p = .0014) (Fig. 2D) labeledplaque burden 23727046 (percent area). The 7 mo-old females did not show any significant difference in Congo red (p = .1011) or 6E10 (p = .1585). Using 6E10 labeling, male mice exposed to 56Fe particle radiation also showed a significant increase of 300 6 56 to 447 6 147 (mean 6 SD, p = .0044) (Fig. 2E) in the average number of plaques after 100 cGy irradiation. Additionally, there was a trend towards larger plaque size (587 6 50 to 628 6 51 mm2, mean 6 SD, p = .052) (Fig. 2F) in the males irradiated with 100 cGy compared to controls (0 cGy). Females did not show any changes in plaque size or number with radiation. To strengthen our histology data and determine whether different forms of Ab were altered after radiation, we prepared soluble and insoluble fractions of homogenized hemibrains and used ELISAs specific for Ab peptides with C-terminals of 40 or 42 (Fig. 
3). For the soluble fraction, there was a significant 35.9 increase in Ab40 levels with 100 cGy radiation in male mice compared to non-irradiated controls by one-way ANOVA [F(2,34) = 4.332 p = .0211] (Fig. 3A). Moreover, male mice showed significant 14.8 and 10.2 increases in concentrations of Ab42 in t.