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Both of exosomes derived from mesenchymal stem cells (MSCs) and glial cell line-derived neurotrophic factor (GDNF) show potential for the treatment of neuropathic pain. Here, the analgesic effects of exosomes derived from bone marrow MSCs (BMSCs) were investigated. BMSCs-derived exosomes were isolated and characterized. Chronic constriction injury (CCI) was constructed to induce neuropathic pain in rats, which were then treated with exosomes. Pain behaviors were evaluated by measuring paw withdrawal thresholds and latency. The changes of key proteins, including cytokines, were explored using Western blot and ELISA. Administration of BMSCs-derived exosomes alleviated neuropathic pain, as demonstrated by the decrease of thermal hyperalgesia and mechanical allodynia, as well as the reduced secretion of pro-inflammatory cytokines in CCI rats. These effects were comparable to the treatment of GDNF alone. Mechanically, the exosomes suppressed the CCI-induced activation of TLR2/MyD88/NF-κB signaling pathway, while GDNF knockdown impaired their analgesic effects on CCI rat. BMSCs-derived exosomes may alleviate CCI-induced neuropathic pain and inflammation in rats by transporting GDNF. [ABSTRACT FROM AUTHOR]

The hyporheic zone (HZ) is a saturated sediment layer connecting groundwater (GW) and surface water (SW) along a riverbed and river channel. The HZ plays an important role in connecting SW and GW in a river ecosystem, thereby helping maintain the ecological health of rivers. Studies on the HZ have therefore increased in many disciplines. This study used the VFLUX 2 software to assess vertical fluid flux in the HZ, in which the Hatch, Kerry, McCallum, and Luce models were applied and compared. The simulations were calibrated against data measured by the US Geological Survey at a water diversion channel within the Walker River Basin in Nevada. Using COMSOL Multiphysics, we developed a two-dimensional coupled numerical model of the saturated seepage and temperature fields, calibrated against measured temperature data. We also determined the vertical seepage velocity and compared the simulations with those of the analytical models in VFLUX 2. The results showed that the temperature field distribution of the HZ is obviously nonuniform in space. With a deeper monitoring point, the thermal response of each temperature measurement pointed to periodic temperature fluctuations of the SW, which exhibited attenuation and hysteresis characteristics. When the vertical flow velocity of GW was sufficiently large, an error in the accuracy of the Kerry model amplitude ratio was observed, regardless of the heat dispersion coefficient used. Under conditions of local GW recharge by SW and a heterogeneous permeability coefficient, the use of the amplitude ratio method is recommended to quantify the vertical GW flow rate in the HZ. [ABSTRACT FROM AUTHOR]

Groundwater–surface water interaction, particularly on exchange fluxes between streams and aquifers, plays a large role in the prerequisite conditions for the study of contaminants and nutrients in the hyporheic zone. One way to quantify these fluxes is by using heat as an environmental tracer. This study quantitatively analyzes the spatial heterogeneity and uncertainty of the vertical turbulent flow of a canopy in the Walker River Basin in Nevada, USA, using the thermal tracer method and the VFLUX software tool. Using the high spatial resolution temperature data measured by the US Geological Survey in the Walker River Basin in Nevada, with the finite element software, COMSOL Multiphysics, it establishes a two-dimensional, full-transect, water-thermal coupling calculation model for the river. The results show that long-term vertical hyporheic flux is between − 111.78 and 86.07 L/m2/d. The average vertical hyporheic flux under seasonal conditions was − 44.35 L/m2/d and − 36.78 L/m2/d in summer and winter, respectively, and the flux exhibits a non-monotonic change with increasing depth. By observing the similarity between the spatial distribution of streambed hyporheic exchange fluxes in winter and summer, as well as the distribution of the streambed profile temperature field, it was found that the spatial distribution of the average streambed hyporheic exchange fluxes can be clearly shown by the streambed profile temperature field in the corresponding season. [ABSTRACT FROM AUTHOR]

Soil thermal conductivity (λ) is an important thermal property which serves as an indicator for the coupling of soil, water, heat, and solutes in a numerical model. The objective of this study is to develop a new empirical model for estimating soil thermal conductivity. There are several methods for estimating λ available, but they are complicated and can produce relatively large errors. Using published datasets, the performance of the new estimate was evaluated along with nine other normalized models, and the advantages and disadvantages of each model and its relevant soil types were analyzed and compared. The results showed that the new empirical model is suitable for studying the thermal conductivities of soils of different textures. In the comparisons, it had the best performance among the ten models considered, with a minimum standard deviation (SD) of 0.074 W m−1 K−1, the coefficient of determination (R2) from 0.929 to 0.983 with a mean of 0.964, and relative error (Re), from 5.210 to 9.900% with a mean of 7.335%. The new model has been shown to improve the reliability of estimation of soil thermal conductivity and has application in agricultural science, environmental science, earth science and engineering research. [ABSTRACT FROM AUTHOR]