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Ginsenoside Rb 3 has been proved to have antidepressant-like effects, which possesses 1 xylose and 3 glucose moieties with 20( S )-protopanaxadiol (PPD) as the aglycone. However, it is commonly accepted that orally ingested ginsenosides can be deglycosylated or partially deglycosylated into active derivatives by the intestinal bacteria. To identify potential antidepressant drug candidates, we compared the antidepressant-like activities between ginsenoside Rb 3 and its four deglycosylated derivatives, Rg 3 , Rh 2 , compound K (C-K), and PPD. Effects of acute (1-day), short chronic (7-days), and longer chronic treatments (14-days) with these ginsenosides (50 and 100 mg/kg, p.o.) on the behavioral changes in the forced swim test (FST), tail suspension test (TST) and open field test were investigated. Serum corticosterone and adrenocorticotropic hormone (ACTH) levels and mouse brain monoamine neurotransmitters 5-HT, NA and DA levels were measured using commercially available competitive enzyme-linked immunosorbent assay (ELISA) kits. Interestingly, C-K showed antidepressant-like activities similar to that of Rb 3 , and Rg 3 displayed antidepressant-like effects at lower dosage and faster time, indicating it has better effects than Rb 3 , whereas Rh 2 and PPD failed to show any effect. Our results also showed, unlike the positive control fluoxetine, Rb 3 , Rg 3 and C-K significantly increased the NA levels in the brain regions of mice exposed to FST but did not affect the 5-HT and DA levels. Moreover, treatment with Rg 3 could reverse swim stress-induced increased levels of serum ACTH and corticosterone. These results suggest that C-K and Rg 3 are the active deglycosylated derivatives, especially the latter compound, which is more potent than Rb 3 and exerts antidepressant-like effects by regulating NA, ACTH and corticosterone levels. [ABSTRACT FROM AUTHOR]

• Dynamic changes of autophagy in the tMCAO mice within 7 d. • Autophagy was strengthened at 1 d of tMCAO induction, and then weakened steadily at 3 d, 5 d and 7 d. • Autophagy positively correlated with the inflammatory response and oxidative stress at 7 d after tMCAO. Ischaemic stroke is attributable to cerebrovascular disease and is associated with high morbidity, disability, mortality and recurrence. Autophagy is a critical mediator and plays dual roles in ischaemic stroke. Autophagy can protect against ischaemic brain injury during the early stage of ischaemic stroke, while excessive autophagy can induce apoptosis and exacerbate brain injury. However, the time-dependent variations in autophagy in ischaemic stroke are unknown. C57BL/6 mice were used to establish a model of temporary middle cerebral artery occlusion and reperfusion (tMCAO). The neurological functional scores and infarct volumes were determined at 1 d, 3 d, 5 d, and 7 d after modelling. The levels of Beclin-1, LC3B, p62, GFAP, TNF-α, IL-6, IL-10, ROS, 4-HNE and 8-OHDG were measured by ELISA, RT-PCR, immunofluorescence analysis and western blotting. The morphology of autophagosomes of ischaemic penumbra was observed by transmission electron microscopy (TEM). Beclin-1, LC3B, ROS, 4-HNE, 8-OHDG, GFAP, TNF-α and IL-6 levels increased (P < 0.01), while p62 and IL-10 levels decreased (P < 0.01) after tMCAO compared to those in the sham group. Beclin-1, LC3B, ROS, 4-HNE, 8-OHDG, GFAP, TNF-α and IL-6 levels were reduced in tMCAO mice at 3 d, 5 d and 7 d (P<0.05), and p62 and IL-10 levels were enhanced (P < 0.05) compared to those at 1 d. In addition, Beclin-1 positively correlated with LC3B, GFAP, TNF-α, IL-6, ROS, 4-HNE and 8-OHDG (P < 0.05), and Beclin-1 negatively correlated with p62 and IL-10 (P < 0.05). The number of autophagosomes was consistent with the expression of autophagy marker proteins, both showing a steady decrease. In summary, autophagy was activated within 7 d of tMCAO induction, and it strengthened at 1 d and then weakened steadily from 3 to 7 d. In addition, this study verified that autophagy positively correlated with the inflammatory response and oxidative stress at 7 d after tMCAO. [ABSTRACT FROM AUTHOR]

Abstract Polyimide (PI) materials are widely used in modern industry due to their excellent flexibility, outstanding performance, and resistance to heat and chemicals. However, thermal degradation of PI materials has become a great challenge while its mechanism and effect on the macroscopic performance still remain uncertain. Here, we comprehensively address this issue by thermally aging PI (TA-PI) films at 300 °C in air for different periods and carrying out microstructure, thermal, dielectric, and space charge characterizations to obtain a deep insight. It was found that oxidation in the aromatic rings, charge transfer complex, and microvoids formed during thermal aging were responsible for the color deepening and opacity. Thermogravimetric analysis revealed that both low-mass volatile and non-volatile pyrolysis products were generated with the prolongation of thermal aging, thus resulting into increased relative permittivity and dielectric loss, decreased breakdown strength (36.6% lower), suppressed space charge, and restricted internal field distortion (≤6%). Low-mass polar molecules are the key to deteriorating the dielectric property of PI materials. The obtained results could provide helpful support for the design and development of PI materials for future engineering applications. Highlights • Effect of thermal aging of PI films on dielectric property and charge evolution are studied. • Low-mass polar molecules are the key to deteriorating the dielectric properties. • Low-mass polar molecules contribute to suppressing space charge and restricted internal field distortion. • Model is proposed to interpret the development of thickness, microvoids, and pyrolysis. [ABSTRACT FROM AUTHOR]

To enhance the insulating performance of presspaper used in power transformers, unmodified nanofibrillated cellulose (UNFC), cationic nanofibrillated cellulose (CNFC), anionic nanofibrillated cellulose (ANFC) and cellulose nanocrystals (CNC) were investigated as the potential nano-additives. Concentration of the nano-additives was 10 wt%. Functional groups and crystallinities of the obtained samples were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Tensile strength, DC volume resistivity, dielectric response and breakdown behavior of the nanomodified and conventional presspaper were analyzed. Results show that nanofibrillated cellulose (NFC) can remarkably enhance tensile strength of insulating presspaper. Compared to ANFC, CNFC has a greater improvement which is mainly ascribed to the electrostatic attraction between the positively charged NFC and negatively charged softwood fiber. In addition to mechanical strength, introduction of nanocellulose can also obviously improve both AC and DC breakdown performances. The reason can be attributed to the reduction of partial discharges inside the composites due to the presence of nanocellulose in the original air voids. Moreover, and importantly, the negative effect of nanocellulose on DC volume resistivity and dielectric response can be neglected. On the basis of the overall performance, we conclude that NFCs are promising nano-additives for insulating presspaper, especially for CNFC. [ABSTRACT FROM AUTHOR]