[en] Bisphenol-A (BPA) is known to be a potent endocrine disrupter. Evidence is emerging that estrogen exerts a rapid influence on hippocampal synaptic plasticity and the dendritic spine density, which requires activation of NMDA receptors. In the present study, we investigated the effects of BPA (ranging from 1 to 1000 nM), focusing on the rapid dynamic changes in dendritic filopodia and the expressions of estrogen receptor (ER) β and NMDA receptor, as well as the phosphorylation of NMDA receptor subunit NR2B in the cultured hippocampal neurons. A specific ER antagonist ICI 182,780 was used to examine the potential involvement of ERs. The results demonstrated that exposure to BPA (ranging from 10 to 1000 nM) for 30 min rapidly enhanced the motility and the density of dendritic filopodia in the cultured hippocampal neurons, as well as the phosphorylation of NR2B (pNR2B), though the expressions of NMDA receptor subunits NR1, NR2B, and ERβ were not changed. The antagonist of ERs completely inhibited the BPA-induced increases in the filopodial motility and the number of filopodia extending from dendrites. The increased pNR2B induced by BPA (100 nM) was also completely eliminated. Furthermore, BPA attenuated the effects of 17β-estradiol (17β-E₂) on the dendritic filopodia outgrowth and the expression of pNR2B when BPA was co-treated with 17β-E₂. The present results suggest that BPA, like 17β-E₂, rapidly results in the enhanced motility and density of dendritic filopodia in the cultured hippocampal neurons with the concomitant activation of NMDA receptor subunit NR2B via an ER-mediated signaling pathway. Meanwhile, BPA suppressed the enhancement effects of 17β-E₂ when it coexists with 17β-E₂. These results provided important evidence suggesting the neurotoxicity of the low levels of BPA during the early postnatal development of the brain.

[en] MoS₂/a-C composite films with various (Mo+S)/C ratios were deposited by medium frequency unbalanced magnetron sputtering. The effects of MoS₂ doping on the microstructure, mechanical and vacuum tribological properties of the films were investigated. Results show that the sp² carbon content in the film increases with increasing (Mo+S)/C ratio from 0 to 0.19, and MoS₂ nanocrystallines are formed in film as (Mo+S)/C ratio increased to 0.07. Consequently, the composite film exhibits decreasing hardness (from 5.2 to 2.5 GPa) and elastic modulus (from 116 to 24 GPa). As the (Mo+S)/C ratio increases from 0 to 0.19, the friction coefficient of the films decreases from 0.18 to 0.008 and sliding time increases from 3 s to more than 3600 s in vacuum. This is mainly attributed to that the films with higher (Mo+S)/C ratios (at least 0.12) are inclined to form the lamellar MoS₂ with low shear strength on the counterface. Furthermore, the composite film with (Mo+S)/C ratio of 0.12 has been investigated in various test environments (air, N₂, vacuum). The average friction coefficient is lower than 0.035 and it exhibits little sensitivity to the test environment. However, the highest and lowest wear rate (about 4 × 10⁻⁷ mm³ Nm⁻¹ and 0.8 × 10⁻⁷ mm³ Nm⁻¹) are obtained in vacuum and N₂, respectively. The environment dependence of the tribological behaviours is related with the lattice orientation of MoS₂ crystalline and the graphitization degree of the film. (paper)

[en] The purposes of the work are to fabricate novel environment-friendly water-based polyamide-imide (PAI)-graphite-LaF₃ bonded solid-lubricating coatings (BSLCs), and investigate the corresponding tribological properties and mechanisms. The experimental results reveal that the preparation of the water-based PAI-graphite-LaF₃ BSLCs has significantly reduced the usage of organic solvent. When the mass percent of nano-LaF₃ is 5 wt%, the water-based PAI-graphite-LaF₃ BSLCs exhibit superior mechanical and tribological properties, which are comparable to those of the reported organic-solvent-based BSLCs. The tribological mechanisms were systematically investigated concerning the failure mechanism, the tribological reactions and structural fluctuations of graphite.