PMC

Photographs of probe 1 test strip (a), probe 1 test strip dipped into 5 mL of KCN solution (100 μM) (b), probe 1 test strip dipped into 5 mL of solution with 0 mL (c), 0.1 mL (d), 0.2 mL (e), and 0.6 mL (f) of bitter almond sample. The photos were taken under illumination of a handheld UV lamp.

Atypical olfactory and cognitive behaviors of amyloid precursor protein (APP)/PS1 mice. (A) Design of the buried food test. (B) Quantitative statistical analysis of latency of 3–4-, 6–7 and 9–10-month-old (mo) APP/PS1 and C57 mice to find the hidden food particle. (C) Design of the fine odor discrimination test. Mice were deprived of water for 24 h and trained to identify distilled water. In one dish, the distilled water was coupled with an odor mixture of mango and almond, in which mango was the main component. The other dish contained bitter water with an odor mixture in which almond was the main component. Different odor proportions of mango and almond were used in the performance test. (D–F) Performance of APP/PS1 and C57 mice at 3–4 (D), 6–7 (E), and 9–10 months of age (F). (G) Design of the Morris water maze (MWM) test. (H) Quantitative statistics of the crossing platform times of APP/PS1 and C57 mice at 3–4, 6–7 and 9–10 months of age. (I–K) Escape latencies of APP/PS1 and C57 mice at 3–4 (I), 6–7 (J) and 9–10 months of age (K). The data are presented as the means ± standard errors of the means (SEMs). *p < 0.05; **p < 0.01.

Mice (15–16 months old) were tested for their ability to discriminate between two odors, almond and coconut, in order to avoid consuming bitter-tasting water. Results represent the average number (± S.E.) of correct responses each genotype made on two sets of tests. Both genotypes performed well on the 100:0 tests, responding correctly on nearly all trials. However, when the task was made more challenging by mixing the odors in a 60:40 ratio to create one stimulus that was mostly almond with some coconut and another that was mostly coconut with some almond, both genotypes were significantly worse at avoiding the bitter water. This decrement of performance was more pronounced in the p44Tg group than in the NT group. Data were analyzed with a repeated measures analysis of variance with genotype (p44Tg vs. NT) as a between group variable and stimulus ratio (100:00 and 60:40) as a within subject variable. The analysis revealed a significant main effect of genotype, F(1,7)=8.39, p=0.02. Overall, group NT made more correct responses than group p44Tg. The main effect of Extract Ratio was also significant, F(1,7)=17.42, p<0.01, reflecting greater accuracy on the 100:0 tests that on the 60:40 tests. The genotype × stimulus ratio interaction was not significant, F(1,7)=2.92, p=0.13.

(A) The design of the fine odor discrimination test. Mice were deprived of water for 2 days and trained to identify distilled water. The distilled water was coupled with an odor mixture of mango and almond; however, mango was the main component. In another dish, bitter water was coupled with a mixture in which almond was the main component. Different proportions of the odors were used for the performance test. (B) Test performance of young (3- to 4-month-old) WT and Wip1-Tg mice shows no differences in fine odor discrimination. Data are mean ± SEM. (C) Test performance of old (16- to 18-month-old) WT and Wip1-Tg mice shows a significantly better fine odor discrimination of Wip1-Tg. Data are mean ± SEM. (D) Representative images and quantification of EdU labeling (2-hour pulse) of neural progenitors. Mice were treated with AraC for 1 month (described in Methods). Insets show colabeling of EdU, DCX, and DAPI. Note a decrease in both EdU- and DCX-positive cells in AraC-treated mice. Data are mean ± SEM. (E) Representative images and quantification of EdU-positive cells 1 month after EdU labeling in control mice and in mice treated with AraC. AraC treatment started right before EdU injection. Data are mean ± SEM. (F) Test performance of AraC-treated and control 1-year-old Wip1-Tg mice. Note that there is a significant reduction in performance after AraC treatment. Data are mean ± SEM. *P < 0.05; ***P < 0.005. Scale bar: 200 μm (D and E); 100 μm (D, inset); 40 μm (E, inset).