[Expression of ubiquitin-specific protease 7 in lung tissue of preterm rats after hyperoxia exposure].

OBJECTIVE: To study the expression and significance of ubiquitin-specific protease 7 (USP7) and the key factors of the Wnt signaling pathway in the lung tissue of preterm rats after hyperoxia exposure. METHODS: A total of 180 preterm neonatal Wistar rats were randomly divided into an air control group, an air intervention group, a hyperoxia control group, and a hyperoxia intervention group, with 45 rats in each group. Lung injury was induced by hyperoxia exposure in the hyperoxia groups. The preterm rats in the intervention groups were given intraperitoneal injection of the USP7 specific inhibitor P5091 (5 mg/kg) every day. The animals were sacrificed on days 3, 5, and 9 of the experiment to collect lung tissue specimens. Hematoxylin-eosin staining was used to observe the pathological changes of lung tissue. RT-PCR and Western blot were used to measure the mRNA and protein expression levels of USP7 and the key factors of the Wnt signaling pathway ß-catenin and α-smooth muscle actin (α-SMA) in lung tissue. RESULTS: The air groups had normal morphology and structure of lung tissue; on days 3 and 5, the hyperoxia control group showed obvious alveolar compression and disordered structure, with obvious inflammatory cells, erythrocyte diapedesis, and interstitial edema. On day 9, the hyperoxia control group showed alveolar structural disorder and obvious thickening of the alveolar septa. Compared with the hyperoxia control group at the corresponding time points, the hyperoxia intervention group had significantly alleviated disordered structure, inflammatory cell infiltration, and bleeding in lung tissue. At each time point, the hyperoxia groups had a significantly lower radial alveolar count (RAC) than the corresponding air groups (P < 0.05), and the hyperoxia intervention group had a significantly higher RAC than the hyperoxia control group (P < 0.05). On days 3, 5, and 9 of the experiment, the hyperoxia groups had significantly higher mRNA expression of USP7 and ß-catenin and protein expression of USP7, ß-catenin, and α-SMA than the corresponding air groups (P < 0.05). Compared with the hyperoxia control group, the hyperoxia intervention group had significant reductions in the mRNA expression of ß-catenin and the protein expression of ß-catenin and α-SMA (P < 0.05), while there were no significant differences in the mRNA and protein expression of USP7 between the hyperoxia intervention and hyperoxia control groups (P > 0.05). There were no significant differences in the mRNA expression of USP7 and ß-catenin and the protein expression of USP7, ß-catenin, and α-SMA between the air intervention and air control groups (P > 0.05). CONCLUSIONS: Hyperoxia exposure can activate the Wnt/ß-catenin signaling pathway, and USP7 may participate in hyperoxic lung injury through the Wnt/ß-catenin signaling pathway. The USP7 specific inhibitor P5091 may accelerate the degradation of ß-catenin by enhancing its ubiquitination, reduce lung epithelial-mesenchymal transition, and thus exert a certain protective effect against hyperoxic lung injury.

Landscape pattern change and its response to anthropogenic disturbance in the Qinling Mountains during 1980 to 2015.

Understanding landscape pattern change and its response to anthropogenic disturbance is of great significance for ecosystem conservation and management. Based on high-precision land use data from 1980 to 2015, we studied the spatial and temporal changes of landscape patterns in the Qinling Mountains and its response to anthropogenic disturbance by using the landscape pattern vulnerability index and human disturbance degree constructed by the landscape pattern index and the surface coverage classification system. The results showed that the degree of landscape fragmentation gradually increased in the Qinling Mountains. The landscape shape became more complex, the degree of landscape aggregation and connectivity decreased, and the spatial distribution of the landscape pattern index showed distinct features of topographic differentiation from 1980 to 2015. The fragility of the landscape pattern in the Qinling Mountains was on a downward trend as a whole. The spatial pattern of the low-vulnerable region had changed significantly, which mainly expanded from Xi'an and Hanzhong to the surrounding areas. The degree of anthropogenic disturbance in the landscape pattern of Qinling Mountains gradually increased. The spatial distribution was "high in the east, low in the west, high in the north-slope, low in the south-slope, high on the periphery, low in the middle". The fragility of landscape pattern, patch density and Shannon diversity index increased with the increases of anthropogenic disturbance, while the aggregation index and maximum patch index decreased. In the past 35 years, the impacts of anthropogenic disturbance, which gradually weakened the vulnerability of landscape pattern, also increased Shannon diversity index and the largest patch index gradually, while it had not significantly changed the patch density and the aggregation index.

Nanoencapsulation of hexavalent chromium with nanoscale zero-valent iron: High resolution chemical mapping of the passivation layer.

Solid phase reactions of Cr(VI) with Fe(0) were investigated with spherical-aberration-corrected scanning transmission electron microscopy (Cs-STEM) integrated with X-ray energy-dispersive spectroscopy (XEDS). Near-atomic resolution elemental mappings of Cr(VI)-Fe(0) reactions were acquired. Experimental results show that rate and extent of Cr(VI) encapsulation are strongly dependent on the initial concentration of Cr(VI) in solution. Low Cr loading in nZVI (<1.0wt%) promotes the electrochemical oxidation and continuous corrosion of nZVI while high Cr loading (>1.0wt%) can quickly shut down the Cr uptake. With the progress of iron oxidation and dissolution, elements of Cr and O counter-diffuse into the nanoparticles and accumulate in the core region at low levels of Cr(VI) (e.g., <10mg/L). Whereas the reacted nZVI is quickly coated with a newly-formed layer of 2-4nm in the presence of concentrated Cr(VI) (e.g., >100mg/L). The passivation structure is stable over a wide range of pH unless pH is low enough to dissolve the passivation layer. X-ray photoelectron spectroscopy (XPS) depth profiling reconfirms that the composition of the newly-formed surface layer consists of Fe(III)-Cr(III) (oxy)hydroxides with Cr(VI) adsorbed on the outside surface. The insoluble and insulating Fe(III)-Cr(III) (oxy)hydroxide layer can completely cover the nZVI surface above the critical Cr loading and shield the electron transfer. Thus, the fast passivation of nZVI in high Cr(VI) solution is detrimental to the performance of nZVI for Cr(VI) treatment and remediation.

Enrichment of Precious Metals from Wastewater with Core-Shell Nanoparticles of Iron.

Large-scale deployment of zero-valent iron nanoparticles for enrichment and recovery of gold from industrial wastewater is reported. Iron nanoparticles have a core-shell structure in which a metallic iron core is enclosed with a thin layer of iron oxides/hydroxides. The two nanocomponents offer synergistic functions for rapid separation, enrichment, and stabilization of metal ions such as Au, Ag, Ni, and Cu. Thanks to the advantages of small size, large surface area, and high reactivity, only a small amount of iron nanoparticles are needed. The recovered nanoparticles thus contain precious metals well above conventional metal ores (e.g., >100 g Au ton-1 ). Cost-effective recovery of precious metals from trace-level sources such as wastewater looks promising.