Isoflurane-Induced Spatial Memory Impairment in Mice is Prevented by the Acetylcholinesterase Inhibitor Donepezil

Although many studies have shown that isoflurane exposure impairs spatial memory in aged animals, there are no clinical treatments available to prevent this memory deficit. The anticholinergic properties of volatile anesthetics are a biologically plausible cause of cognitive dysfunction in elderly subjects. We hypothesized that pretreatment with the acetylcholinesterase inhibitor donepezil, which has been approved by the Food and Drug Administration (FDA) for the treatment of Alzheimer's disease, prevents isoflurane-induced spatial memory impairment in aged mice. In present study, eighteen-month-old mice were administered donepezil (5 mg/kg) or an equal volume of saline by oral gavage with a feeding needle for four weeks. Then the mice were exposed to isoflurane (1.2%) for six hours. Two weeks later, mice were subjected to the Morris water maze to examine the impairment of spatial memory after exposure to isoflurane. After the behavioral test, the mice were sacrificed, and the protein expression level of acetylcholinesterase (AChE), choline acetylase (ChAT) and α7 nicotinic receptor (α7-nAChR) were measured in the brain. Each group consisted of 12 mice. We found that isoflurane exposure for six hours impaired the spatial memory of the mice. Compared with the control group, isoflurane exposure dramatically decreased the protein level of ChAT, but not AChE or α7-nAChR. Donepezil prevented isoflurane-induced spatial memory impairments and increased ChAT levels, which were downregulated by isoflurane. In conclusions, pretreatment with the AChE inhibitor donepezil prevented isoflurane-induced spatial memory impairment in aged mice. The mechanism was associated with the upregulation of ChAT, which was decreased by isoflurane

Atomistic Control in Molecular Beam Epitaxy Growth of Intrinsic Magnetic Topological Insulator MnBi2Te4

Intrinsic magnetic topological insulators have emerged as a promising platform to study the interplay between topological surface states and ferromagnetism. This unique interplay can give rise to a variety of exotic quantum phenomena, including the quantum anomalous Hall effect and axion insulating states. Here, utilizing molecular beam epitaxy (MBE), we present a comprehensive study of the growth of high-quality MnBi2Te4 thin films on Si (111), epitaxial graphene, and highly ordered pyrolytic graphite substrates. By combining a suite of in-situ characterization techniques, we obtain critical insights into the atomic-level control of MnBi2Te4 epitaxial growth. First, we extract the free energy landscape for the epitaxial relationship as a function of the in-plane angular distribution. Then, by employing an optimized layer-by-layer growth, we determine the chemical potential and Dirac point of the thin film at different thicknesses. Overall, these results establish a foundation for understanding the growth dynamics of MnBi2Te4 and pave the way for the future applications of MBE in emerging topological quantum materials.Comment: 20 pages, 4 figure

Gut Symbionts alleviate Mash Through a Secondary Bile acid Biosynthetic Pathway

The gut microbiota has been found to play an important role in the progression of metabolic dysfunction-associated steatohepatitis (MASH), but the mechanisms have not been established. Here, by developing a click-chemistry-based enrichment strategy, we identified several microbial-derived bile acids, including the previously uncharacterized 3-succinylated cholic acid (3-sucCA), which is negatively correlated with liver damage in patients with liver-tissue-biopsy-proven metabolic dysfunction-associated fatty liver disease (MAFLD). By screening human bacterial isolates, we identified Bacteroides uniformis strains as effective producers of 3-sucCA both in vitro and in vivo. By activity-based protein purification and identification, we identified an enzyme annotated as β-lactamase in B. uniformis responsible for 3-sucCA biosynthesis. Furthermore, we found that 3-sucCA is a lumen-restricted metabolite and alleviates MASH by promoting the growth of Akkermansia muciniphila. together, our data offer new insights into the gut microbiota-liver axis that may be leveraged to augment the management of MASH

High-throughput calculation screening for new silicon allotropes with monoclinic symmetry

A total of 87 new monoclinic silicon allotropes are systematically scanned by a random strategy combined with group and graph theory and high-throughput calculations. The new allotropes include 13 with a direct or quasi-direct band gap and 12 with metallic characteristics, and the rest are indirect band gap semiconductors. More than 30 of these novel monoclinic Si allotropes show bulk moduli greater than or equal to 80 GPa, and three of them show even greater bulk moduli than diamond Si. Only two of the new Si allotropes show a greater shear modulus than diamond Si. The crystal structures, stability (elastic constants, phonon spectra), mechanical properties, electronic properties, effective carrier masses and optical properties of all 87 Si monoclinic allotropes are studied in detail. The electron effective masses ml of five of the new allotropes are smaller than that of diamond Si. All of these novel monoclinic Si allotropes show strong absorption in the visible spectral region. Taken together with their electronic band gap structures, this makes them promising materials for photovoltaic applications. These investigations greatly enrich the current knowledge of the structure and electronic properties of silicon allotropes

BN Polymorphs in Hexagonal 2–7 Stacking Orders: First-Principles and High-Throughput Study

BN polymorphs are important basic materials in superhard materials, as well as in other industrial fields and in microelectronics. The ground-state phase of BN polymorphs has a 3C stacking order. In addition to 3C, eight BN polymorphs (2H, 4H, 5H, 6H-I, 6H-II, 7H-I, 7H-II, and 7H-III) are produced by a random sampling strategy combined with group theory and graph theory (RG2) in this work. It is found that the stack order of 2–7H BN polymorphs is basically similar to that of 3C BN, although with a slight difference. The calculated total energy of these 2–7H BN polymorphs is only 4–17 meV/atoms higher than that of 3C BN, and they are all dynamically and mechanically stable. In addition, their thermal stability at 1000 K is also studied by ab initio molecular dynamics (AIMD) techniques. A combination of tensile stress and hardness is sufficient to prove that BN is a superhard material in 2–7H BN polymorphs. The band gaps of 2–7H BN polymorphs are in the range of 6.19–6.98 eV, and they can be considered as promising ultrawide-bandgap semiconductors. Finally, the anisotropy in Young’s modulus and X-ray diffraction (XRD) patterns of 2–7H BN polymorphs are also investigated in this work

Influence of Additive Chemistry on the Tribological Behavior of Steel/Copper Friction Pairs

Tribological properties of five anti-wear additives for a steel-copper contact were investigated. It was found that the tribological performances are closely related to the molecular structure of additives. The protic ionic liquid anti-wear additive AW316 exhibits the best tribological performance with the lowest mean friction coefficient of 0.082, and the smallest wear volume, which is more than one order of magnitude smaller than base oil. Transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) tests reveal that a 10–15 nm thickness uniform boundary lubrication film composed of oxides, phosphates, and cuprous oxide was formed on the copper disc, which was responsible for its outstanding tribological performances