<i>cis</i>-2,3-Disubstituted Cyclopropane 1,1-Diesters in [3 + 2] Annulations with Aldehydes: Highly Diastereoselective Construction of Densely Substituted Tetrahydrofurans

A series of <i>cis</i>-2,3-disubstituted cyclopropane 1,1-diesters were examined in the AlCl₃-promoted [3 + 2]-annulations with aldehydes. In this reaction, these <i>cis</i>-cyclopropanes displayed reactivities starkly different from their <i>trans</i> counterparts in terms of the high chemical yields (up to 98%) and provided the desired annulation products with excellent diastereomeric purity. This protocol provides a facile and highly stereoselective way to construct synthetically useful pentasubstituted tetrahydrofurans not easily accessible using other methods

<i>cis</i>-2,3-Disubstituted Cyclopropane 1,1-Diesters in [3 + 2] Annulations with Aldehydes: Highly Diastereoselective Construction of Densely Substituted Tetrahydrofurans

A series of <i>cis</i>-2,3-disubstituted cyclopropane 1,1-diesters were examined in the AlCl₃-promoted [3 + 2]-annulations with aldehydes. In this reaction, these <i>cis</i>-cyclopropanes displayed reactivities starkly different from their <i>trans</i> counterparts in terms of the high chemical yields (up to 98%) and provided the desired annulation products with excellent diastereomeric purity. This protocol provides a facile and highly stereoselective way to construct synthetically useful pentasubstituted tetrahydrofurans not easily accessible using other methods

Expression of tau40 induces increased Iba1.

<p>In cultured rat microglia, the plasmid of human tau40 (441 amino acids) or vector was transfected for 24 h. Then the levels of total tau probed by R134d and Iba1, a marker of microglial activation, were measured by Western blotting (A) and quantitative analysis (B) respectively. The alteration of Iba1 was normalized against DM1A. The experiments were repeated at least three times and data were presented as means ± S.D.. * <i>p</i><0.05 versus vector-transfected cells.</p

Activation of microglia in the brains of rats and mice with aging.

<p>Microglia in the cortex of 4- and 14-month-old SD rats (A), 3- and 12-month-old C57BL/6 mice (D) were immunostained by Iba1, a marker of microglia (Scale bar = 100 µm). The fractal dimension value analysis was used to evaluate the activation of microglia in the brains of different group of animals. Lower fractal dimension value indicates higher activity of microglia. We divided the fractal dimension value of the microglia into four grades (>1.3, 1.2–1.3, 1.1–1.2, <1.1), and the percentages of microglia with different grades were shown in B and E, the differences of the same grade between the different age of animals were shown in C and F (n>43 cells/group). Data were presented as means ± S.D.. * <i>p</i><0.05, ** <i>p</i><0.01 versus 4-month-old SD rats/3-month-old C57BL/6 mice.</p

Expression of tau40 promotes migration of microglia.

<p>In cultured rat microglia, the plasmid of human tau40-EGFP or vector-EGFP was transfected for 24 h. Then <i>in vitro</i> scratch assay was performed and the images of migration were captured at 0 h, 6 h, 12 h and 24 h after scratching with confocal microscope (A) (Scale bar = 100 µm). The migration rate of microglia was quantified by the distance that the EGFP positive cells moved from the edge of the scratch towards the center per hour. The average migration rates of the EGFP positive microglia in 0–6 h, 6–12 h and 12–24 h were calculated from three independent experiments (B). Data were presented as means ± S.D.. * <i>p</i><0.05, ** <i>p</i><0.01 versus vector-transfected cells.</p

Expression of tau40 induces membranous accumulation of phosphorylated tau, simultaneously with inhibition of PP2A and activation of ERK and GSK-3β.

<p>In cultured rat microglial cells, the plasmid of human tau40-EGFP (T) or vector-EGFP (V) was transfected. 24 h later, triple immunofluorescence imaging was performed. The nucleus was stained with Hoechst (blue) and the phosphorylated tau was probed by pS396 (an antibody recognizing phosphorylated tau at Ser396) (red). Then cells were observed by confocal microscope (A) (Scale bar = 20 µm). The membranous (m) and cytoplasma (p) fractions were isolated as described in the method and the level of pS396 in the two fractions was analyzed by Western blotting (B) and quantitative analysis (C). The levels of PP2Ac, p-PP2Ac (Y307), ERK, p-ERK, GSK-3β and p-GSK-3β (S9) were probed and measured by Western blotting (D) and quantitative analysis (E). The data were representative of three independent experiments and were presented as means ± S.D.. * <i>p</i><0.05 versus vector-transfected cells.</p

Both total tau and phosphorylated tau increase in activated microglia.

<p>Microglia in the brain slices were co-immunostained with Iba1 (green) and Tau46 (an antibody recognizing total tau) or AT8 (an antibody recognizing phosphorylated tau at Ser202/Thr205) (red). In contrast with the ramified microglia (arrow heads), ameboid microglia (arrows) showed increased total tau (A, C) and the phosphorylated tau (E, G) (Scale bar = 20 µm). The relative levels of integrated optical density (IOD) of Tau46/AT8 in microglia with different grades of fractal dimension value were shown in B, D, F, H. Data were presented as means ± S.D.. ** <i>p</i><0.01 versus microglia with fractal dimension value <1.1.</p