Hypoxia ischemia results in blood brain barrier damage via AKT/GSK-3ß/CREB pathway in neonatal rats.

Previous studies have showed that the permeability of blood brain barrier (BBB) increased after hypoxia ischemia (HI). The current research uncovered the mechanism of altered BBB permeability after hypoxic-ischemic brain damage (HIBD) through AKT/GSK-3ß/CREB signaling pathway in neonatal rats. Firstly, Magnetic resonance imaging (MRI) combined with hematoxylin-eosin (H&E) staining was used to assess brain injury. Initial findings showed abnormal signals in T2-weighted imaging (T2WI) and diffusion weighted imaging (DWI). Changes also happened in the morphology of nerve cells. Subsequently, we found that BBB damage is manifested as leakage of immunoglobulin G (IgG) and destruction of BBB-related proteins and ultrastructure. Meanwhile, the levels of matrix metalloproteinase-9 (MMP-9) significantly increased at 24 h after HIBD compared to a series of time points. Additionally, immunohistochemical (IHC) staining combined with Western blot (WB) was used to verify the function of the AKT/GSK-3ß/CREB signaling pathway in BBB damage after HI in neonatal rats. Results showed that less Claudin-5, ZO-1, p-AKT, p-GSK-3ß and p-CREB, along with more MMP-9 protein expression were visible on the damaged side of the cerebral cortex in the HIBD group in contrast to the sham and HIBD + SC79 groups. Together, our findings demonstrated that HI in neonatal rats might upregulate the levels of MMP-9 protein and downregulate the levels of Claudin-5 and ZO-1 by inhibiting the AKT/GSK-3ß/CREB pathway, thus disrupting the BBB, which in turn aggravates brain damage after HI in neonatal rats.

Exploring the limits of metasurface polarization multiplexing capability based on deep learning.

Metasurfaces provide a new approach for planar optics and thus have realized multifunctional meta-devices with different multiplexing strategies, among which polarization multiplexing has received much attention due to its convenience. At present, a variety of design methods of polarization multiplexed metasurfaces have been developed based on different meta-atoms. However, as the number of polarization states increases, the response space of meta-atoms becomes more and more complex, and it is difficult for these methods to explore the limit of polarization multiplexing. Deep learning is one of the important routes to solve this problem because it can realize the effective exploration of huge data space. In this work, a design scheme for polarization multiplexed metasurfaces based on deep learning is proposed. The scheme uses a conditional variational autoencoder as an inverse network to generate structural designs and combines a forward network that can predict meta-atoms' responses to improve the accuracy of designs. The cross-shaped structure is used to establish a complicated response space containing different polarization state combinations of incident and outgoing light. The multiplexing effects of the combinations with different numbers of polarization states are tested by utilizing the proposed scheme to design nanoprinting and holographic images. The polarization multiplexing capability limit of four channels (a nanoprinting image and three holographic images) is determined. The proposed scheme lays the foundation for exploring the limits of metasurface polarization multiplexing capability.

Magnetic Resonance Imaging Combined with Histological Techniques for Dynamic Assessment of Cytotoxic Edema after Cerebral Ischemia-Reperfusion Injury.

BACKGROUND: Reperfusion therapy after ischemic cerebral stroke may cause cerebral ischemia-reperfusion injury (CIRI), and cerebral edema is an important factor that may aggravate CIRI. Our study aimed to dynamically monitor the development of early cytotoxic edema after CIRI by magnetic resonance imaging (MRI) and to validate it using multiple histological imaging methods. METHODS: Male Sprague Dawley rats were divided into sham and CIRI groups. T2-weighted imaging (T2WI) and diffusion-weighted imaging (DWI)-MRI scans were performed in the sham and CIRI groups after reperfusion. Relative apparent diffusion coefficient (rADC) values were calculated and the midline shift (MLS) was measured. A series of histological detection techniques were performed to observe changes in the cerebral cortex and striatum of CIRI rats. Correlation analysis of rADC values with aquaporin-4 (AQP4) and sodium-potassium-chloride cotransport protein 1 (Na+-K+-2Cl-- cotransporter 1; NKCC1) was performed. RESULTS: rADC values began to increase and reached a relatively low value in the cerebral cortex and striatum at 24 h after reperfusion, and the MLS reached relatively high values at 24 h after reperfusion (all p < 0.05). Hematoxylin-eosin (HE) staining showed that the nerve cells in the cortex and striatum of the sham group were regular in morphology and neatly arranged, and in the CIRI-24 h group were irregular, disorganized, and loosely structured. Using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, the number of TUNEL+ cells in the ischemic cortex and striatum in CIRI-24 h group was shown to increase significantly compared with the sham group (p < 0.05). Transmission electron microscopy showed that the perivascular astrocytic foot processes were swollen in the cortex and striatum of the CIRI-24 h group. Pearson correlation analysis demonstrated that rADC values were negatively correlated with the number of anti-glial fibrillary acidic protein (GFAP)+AQP4+ and GFAP+NKCC1+ cells of the CIRI rats. CONCLUSIONS: MRI combined with histological techniques can dynamically assess cytotoxic edema after CIRI, in a manner that is clear and intuitive for scientific researchers and clinicians, and provides a scientific basis for the application of MRI techniques for monitoring the dynamic progress of CIRI.

Effect of grafted graphene nanosheets on morphology evolution and conductive behavior of poly(methyl methacrylate)/poly(styrene-co-acrylonitrile) blends during isothermal annealing.

A facile method was developed for directly grafting poly(methyl methacrylate) (PMMA) to graphene oxide (GO) without surface modification, with the resultant insulating PMMA-g-GO nanosheets further reduced in situ to give conductive grafted reduced graphene oxide (RGO) nanosheets. The effect of PMMA-g-RGO nanosheets on the morphological evolution and conductive behavior of partially miscible blends of poly(methyl methacrylate)/poly (styrene-co-acrylonitrile) (PMMA/SAN) upon annealing above their phase-separation temperature was investigated using phase-contrast microscopy (PCM) with a real-time online digital picoammeter. With phase separation of the blend matrix, the well-dispersed PMMA-g-RGO nanosheets in the homogeneous matrix preferentially migrated to the SAN-rich phase and showed remarkably little aggregation. Surface grafting of PMMA-g-RGO might inhibit the aggregation of nanosheets in the blend matrix and weaken the retardation effect of nanosheets on the morphology evolution of the blend matrix. Furthermore, the percolation behavior of dynamic resistivity for ternary nanocomposites was attributed to the formation of a PMMA-g-RGO conductive network in the SAN-rich phase. The activation energy of conductive pathway formation was closer to the activation energy of flow for PMMA than that of SAN.

Phase separation behavior of poly(methyl methacrylate)/poly(styrene-co-maleic anhydride) in the presence of hollow silica nanotubes.

The phase separation behavior of poly(methyl methacrylate) (PMMA)/poly(styrene-co-maleic anhydride) (SMA) blends with and without one-dimensional hollow silica nanotubes (HSNTs) was investigated using time-resolved small-angle laser light scattering. During isothermal annealing over a range of 100 °C above the glass transition temperature, the Arrhenius equation is applicable to describe the temperature dependence of phase separation behavior at the early and late stages of spinodal decomposition (SD) for unfilled and filled PMMA/SMA systems. The mechanical barrier effect of HSNTs on the macromolecular chain diffusion of the blend matrix may retard the concentration fluctuation at the early stage and slow down the domain coarsening at the late stage of SD phase separation for the blend matrix to result in the decrease of apparent diffusion coefficient D app, the postponement of the relaxation time and the decline of temperature sensitivity for the phase separation rate.