Proposal of Crack Propagation Criterion Considered Constraint Effect under Extremely Low Cycle Fatigue; Evaluation by 1.5T-CT Specimen

The prediction of fracture behavior under extremely low cycle fatigue due to excessive loading is necessary for the life assessment of structures. This study evaluates the validity of the crack propagation criterion proposed in a previous study by performing generation phase and application phase analysis based on the results of fracture tests on a 1.5T-CT specimen (SGV410). The analysis show that the crack propagation criterion in the previous study predicted the experimental behavior well, however crack shape was incomplete in reproducing the crack shape

Changes in expression of aquaporin-4 and aquaporin-9 in optic nerve after crushing in rats.

The purpose of this study was to determine the temporal and spatial changes in the expression of AQP4 and AQP9 in the optic nerve after it is crushed. The left optic nerves of rats were either crushed (crushed group) or sham operated (sham group), and they were excised before, and at 1, 2, 4, 7, and 14 days later. Four optic nerves were pooled for each time point in both groups. The expression of AQP4 and AQP9 was determined by western blot analyses. Immunohistochemistry was used to determine the spatial expression of AQP4, AQP9, and GFAP in the optic nerve. Optic nerve edema was determined by measuring the water content in the optic nerve. The barrier function of the optic nerve vessels was determined by the extravasated Evans blue dye on days 7 and 14. The results showed that the expression of AQP4 was increased on day 1 but the level was significantly lower than that in the sham group on days 4 and 7 (P<0.05). In contrast, the expression of AQP9 gradually increased, and the level was significantly higher than that in the sham group on days 7 and 14 (P<0.05, Tukey-Kramer). The down-regulation of AQP4 was associated with crush-induced optic nerve edema, and the water content of the nerve was significantly increased by 4.3% in the crushed optic nerve from that of the untouched fellow nerve on day 7. The expression of AQP4 and GFAP was reduced at the crushed site where AQP4-negative and AQP9-positive astrocytes were present. The barrier function was impaired at the crushed site on days 7 and 14, restrictedly where AQP4-negative and AQP9-positive astrocytes were present. The presence of AQP9-positive astrocytes at the crushed site may counteract the metabolic damage but this change did not fully compensate for the barrier function defect

Immunohistochemistry for AQP4 (A) and AQP9 (B) expression before, and 1, 4, 7, and 14 days after crushing the optic nerves.

<p>Representative photographs from 3 independent samples are presented. Arrows indicate crush sites. A. Immunoreactivity to AQP4 is increased at the cracks (arrows) caused by the crushing on day 1. Immunoreactivities to AQP4 and GFAP are reduced at the crush sites (arrows) on day 4 and thereafter. Bar  = 500 µm. B. Immunoreactivity to AQP9 is faint along the crush-induced cracks (arrows) on day 1. However, immunoreactivity to AQP9 is intensified at the crush sites on day 4 and thereafter. Bar  = 500 µm.</p

Western blot analyses for AQP4 (A), AQP9 (B), and GFAP (C).

<p>A.-C. Changes in the protein levels of AQP4 (A), AQP9 (B), and GFAP (C). Four optic nerves (4 mm in length) centered on the crush sites were serially excised and pooled as one sample at each time point. Proteins were extracted from the pooled samples and assays were run in triplicate at each time point using the pooled samples. D. Changes of water content in the optic nerve. Water content is expressed as percentages to the wet weight (n = 4 at each time point). Data are the means ± standard deviations (SDs). Asterisks indicate significant differences between the crushed optic nerve and the untouched fellow nerve at each time point (<i>P</i><0.05, ANOVA followed by Tukey-Kramer).</p

Immunohistochemistry for CD68 in the optic nerve.

<p>There is a cellular accumulation indicated by DAPI at the crushed sites of the optic nerve. Some of the cells are positively stained with CD68 suggesting that there is a recruitment of microglia/macrophages to the crushed sites. Bar  = 100 µm.</p

Representative western blots for aquaporin-4 (AQP4), aquaporin-9 (AQP9), and GFAP in extracts from the optic nerves after they were crushed (A) and sham (B) operated.

<p>Tubulin was used as an internal control.</p

Filopodium-derived vesicles produced by MIM enhance the migration of recipient cells

Extracellular vesicles (EVs) are classified as large EVs (l-EVs, or microvesicles) and small EVs (s-EVs, or exosomes). S-EVs are thought to be generated from endosomes through a process that mainly depends on the ESCRT protein complex, including ALG-2 interacting protein X (ALIX). However, the mechanisms of l-EV generation from the plasma membrane have not been identified. Membrane curvatures are generated by the bin-amphiphysin-rvs (BAR) family proteins, among which the inverse BAR (I-BAR) proteins are involved in filopodial protrusions. Here, we show that the I-BAR proteins, including missing in metastasis (MIM), generate l-EVs by scission of filopodia. Interestingly, MIM-containing l-EV production was promoted by in vivo equivalent external forces and by the suppression of ALIX, suggesting an alternative mechanism of vesicle formation to s-EVs. The MIM-dependent l-EVs contained lysophospholipids and proteins, including IRS4 and Rac1, which stimulated the migration of recipient cells through lamellipodia formation. Thus, these filopodia-dependent l-EVs, which we named as filopodia-derived vesicles (FDVs), modify cellular behavior

The Cosmic Infrared Background ExpeRiment-2: First Flight Status Report

240th meeting of the AAS, on June 12–16, Californi