Toxicity and chemical characterization of shale gas wastewater discharged to the receiving water: Evidence from toxicity identification evaluation.

Flowback and produced water (FPW) generated from shale gas extraction is a complex mixture consisting of injected drilling fluid, deep formation water, and byproducts of downhole reactions. Limited knowledge is available regarding the impact of discharged FPW on surface water in China. With the development of shale gas exploitation, this emphasizes an urgent need for comprehensive assessments and stringent regulations to ensure the safe disposal of shale gas extraction-related wastewater. Herein, we explored potential impacts of treated shale gas wastewater discharged into a local river in southwest China through toxicity identification evaluation (TIE). Results revealed that organics and particulates significantly contributed to the overall toxicity of the treated FPW wastewater. Through target and suspect chemical analyses, various categories of organic contaminants were detected, including alkanes, aromatic hydrocarbons, biocides, phenols, and phthalates. Furthermore, non-target analysis uncovered the presence of surfactant-related contaminants in tissues of exposed organisms, but their contribution to the observed toxicity was unclear due to the lack of effect data for these compounds. Higher toxicity was found at the discharge point compared with upstream sites; however, the toxicity was rapidly mitigated due to dilution in the receiving river, posing little impact on downstream areas. Our study highlighted the importance of monitoring toxicity and water quality of FPW effluent even though dilution could be a viable approach when the water volume in the discharge was small.

Toxicity identification evaluation for hydraulic fracturing flowback and produced water during shale gas exploitation in China: Evidence from tissue residues and gene expression.

Hydraulic fracturing flowback and produced water (HF-FPW) from shale gas extraction processes is a highly complex medium with potential threats to the environment. Current research on ecological risks of FPW in China is limited, and the link between major components of FPW and their toxicological effects on freshwater organisms is largely unknown. By integrating chemical and biological analyses, toxicity identification evaluation (TIE) was used to reveal causality between toxicity and contaminants, potentially disentangling the complex toxicological nature of FPW. Here, FPW from different shale gas wells, treated FPW effluent, and a leachate from HF sludge were collected from southwest China, and TIE was applied to obtain a comprehensive toxicity evaluation in freshwater organisms. Our results showed that FPW from the same geographic zone could cause significantly different toxicity. Salinity, solid phase particulates, and organic contaminants were identified as the main contributors to the toxicity of FPW. In addition to water chemistry, internal alkanes, PAHs, and HF additives (e.g., biocides and surfactants) were quantified in exposed embryonic fish by target and non-target tissue analyses. The treated FPW failed to mitigate the toxicity associated with organic contaminants. Transcriptomic results illustrated that organic compounds induced toxicity pathways in FPW-exposed embryonic zebrafish. Similar zebrafish gene ontologies were affected between treated and untreated FPW, again confirming that sewage treatment did not effectively remove organic chemicals from FPW. Thus, zebrafish transcriptome analyses revealed organic toxicant-induced adverse outcome pathways and served as evidence for TIE confirmation in complex mixtures under data-poor scenarios.

miR-199a-5p from bone marrow mesenchymal stem cell exosomes promotes the proliferation of neural stem cells by targeting GSK-3ß.

Bone marrow mesenchymal stem cell (BMSC)-derived exosomes are a promising therapeutic agent for human disease, but their effects on neural stem cells (NSCs) subject to spinal cord ischaemia-reperfusion injury (SCIRI) remain unknown. Here, we examine the impact of miR-199a-5p-enriched exosomes derived from BMSCs on NSC proliferation. We establish a rat model of aortic cross-clamping to induce SCIRI in vivo and a primary NSC model of oxygen-glucose deprivation/reoxygenation (OGD/R) to simulate SCIRI in vitro. CCK8, EdU, and BrdU assays are performed to evaluate the proliferation of NSCs. Hematoxylin and eosin (H&E) staining is used to determine the number of surviving neurons. The Basso, Beattie, and Bresnahan (BBB) scale and inclined plane test (IPT) are used to evaluate hind limb motor function. DiO-labelled exosomes are efficiently internalized by NSCs and increase ectopic amounts of miR-199a-5p, which promotes the proliferation of NSCs. In contrast, exosomes derived from miR-199a-5p-depleted BMSCs exert fewer beneficial effects. MiR-199a-5p targets and negatively regulates glycogen synthase kinase 3ß (GSK-3ß) and increases nuclear ß-catenin and cyclin D1 levels. miR-199a-5p inhibition reduces the total number of EdU-positive NSCs after OGD/R, but the GSK-3ß inhibitor CHIR-99021 reverses this effect. In vivo, intrathecal injection of BMSC-derived exosomes increases the proliferation of endogenous spinal cord NSCs after SCIRI. In addition, more proliferating NSCs are found in rats intrathecally injected with exosomes overexpressing miR-199a-5p. In summary, miR-199a-5p in BMSC-derived exosomes promotes NSC proliferation via GSK-3ß/ß-catenin signaling.

Effect of combined epidural-general anesthesia on long-term survival of patients with colorectal cancer: a meta-analysis of cohort studies.

PURPOSE: This study aimed to analyze the long-term survival of patients with colorectal cancer after receiving combined epidural-general anesthesia (EGA) or general anesthesia (GA) alone. METHODS: The PubMed, MEDLINE, Web of Science, Cochrane Library, and Embase databases were used to search for cohort studies that explored the differences between the effects of EGA and GA on overall survival (OS) and recurrence-free survival (RFS) of patients with colorectal cancer. The hazard ratios (HRs) and their 95% confidence intervals (95%CIs) were used as indicators to evaluate the strength of the effects and were pooled. RESULTS: Nine studies were included in the meta-analysis. EGA improved the OS of patients with colorectal cancer compared with GA (HR = 0.904, 95%CI 0.871-0.938, P < 0.05). In the subgroup analysis, EGA was more protective for OS of patients with colon cancer than GA (HR = 0.840, 95%CI 0.732-0.963, P < 0.05), but not for OS of patients with rectal cancer (HR = 0.764, 95%CI 0.398-1.469, P > 0.05). Additionally, EGA could not further prolong RFS in patients with colorectal cancer (HR = 1.015, 95%CI 0.942-1.093, P > 0.05), which was the same in the subgroup analysis of patients with colon cancer (HR = 0.908, 95%CI 0.760-1.085, P > 0.05). CONCLUSION: EGA could improve the OS of patients with colorectal cancer, especially those with colon cancer, but it could not improve the OS in the subgroup of patients with rectal cancer. This difference may be due to the immune protective function of the parasympathetic nerve innervating the intestinal tubes above the splenic flexure retained by EGA. Additionally, although EGA has a protective effect on RFS in patients with colorectal cancer, the difference was not significant.  The design of this analysis is registered and displayed in the PROSPERO database (CRD42021274864).

Identification and characterization of RNA duplex unwinding and ATPase activities of an alphatetravirus superfamily 1 helicase.

Dendrolimus punctatus tetravirus (DpTV) belongs to the genus omegatetravirus of the Alphatetraviridae family. Sequence analysis predicts that DpTV replicase contains a putative helicase domain (Hel). However, the helicase activity in alphatetraviruses has never been formally determined. In this study, we determined that DpTV Hel is a functional RNA helicase belonging to superfamily-1 helicase with 5'-3' dsRNA unwinding directionality. Further characterization determined the length requirement of the 5' single-stranded tail on the RNA template and the optimal reaction conditions for the unwinding activity of DpTV Hel. Moreover, DpTV Hel also contains NTPase activity. The ATPase activity of DpTV Hel could be significantly stimulated by dsRNA, and dsRNA could partially rescue the ATPase activity abolishment caused by mutations. Our study is the first to identify an alphatetravirus RNA helicase and further characterize its dsRNA unwinding and NTPase activities in detail and should foster our understanding of DpTV and other alphatetraviruses.