Comparison of the values of MRI diffusion kurtosis imaging and diffusion tensor imaging in cerebral astrocytoma grading and their association with aquaporin-4.

OBJECTIVE: To compare the value of MRI diffusion kurtosis imaging (DKI) and diffusion tensor imaging (DTI) in grading cerebral astrocytomas and to analyze the correlation of respective parameters with aquaporin-4 (AQP4) expression. METHODS: Sixty patients with cerebral astrocytoma, including low-grade astrocytomas (LGA, n = 25) and high-grade astrocytomas (HGA, n = 35), were studied. The values of DKI parameters (mean kurtosis [MK], radial kurtosis [Kr], and axial kurtosis [Ka]) and DTI parameters (fractional anisotropy, mean diffusivity [MD]) corrected by contralateral normal-appearing white matter in the solid parts of the tumors and peritumoral edema were compared. Receiver operating characteristic curves were used to identify the best parameters. Spearman correlation analysis was conducted to assess the correlation of AQP4 expression with each parameter value. RESULTS: MK, Ka, and Krvalues were significantly higher whereas MD values were significantly lower in the solid parts of HGA, as compared to those of LGA. MK value in peritumoral edematous tissue was significantly higher in HGA as compared to that in LGA. Ka (0.889) had the largest area under the curve (AUC), followed by MK (0.840), Kr (0.750), and MD (0.764). The AUC of Kaand MK was significantly higher than that of MD. Optimal thresholds for MK, Ka, Kr, and MD for differentiating the two groups were 0.490, 0.525, 0.432, and 1.493, respectively. The AQP4 expression in the solid parts of the tumors was significantly higher in HGAs. MK, Kr, Kavalues positively correlated with the AQP4 expression, whereas MD showed a slight negative correlation with AQP4. CONCLUSION: Use of DKI improved grading of cerebral astrocytomas when compared with DTI. DKI parameters appeared to reflect the level of AQP4 expression in astrocytomas.

Identification of priority areas for territorial space ecological restoration in arid area of Northwest China: A case study of Zhangye City in Heihe River basin.

Determining priority areas for territorial ecological restoration in the arid region of Northwest China based on the holistic protection and systematic governance is an important measure to build solid national ecological security barrier and promote the construction of territorial ecological civilization. Taking Zhangye City, a typical arid area city in Northwest China, as an example, we constructed the research framework of "ecological network-ecological sensitivities-ecological degradation" from two aspects of internal defects and external threats of ecological networks by using circuit theory and assessment methods of ecological service function importance, ecological sensitivity, and ecological degradation. We then identified the priority areas of territorial ecological restoration in northwest arid region and put forward the restoration strategies. The results showed that the priority areas of ecological restoration in Zhangye City were concentrated in the artificial shelterbelt along rivers and the plain-desert-oasis transition zone with fragile ecology and strong human interference. The ecological network of the study area included 39 ecological sources and 99 ecological corridors, and the highly sensitive and degraded areas were 1595.40 and 6.65 km2. Based on the internal defects and external threats of the ecological network, we identified 31 ecological pinch points, 7 obstacle points, and 753.56 km2 ecological source areas in the territorial spatial ecological restoration priority area. These areas were related to the connectivity of the ecological network internally and the stability maintenance of the ecosystem outwards, and were the areas to restoration in the future. Following the concept of overall protection and system restoration of territorial space, we put forward the idea of territorial space restoration by integrating internal defects and external threats of ecological network, which could provide scientific decision-making basis for comprehensive ecosystem management and territorial optimization of Zhangye City.

[Establishment and evaluation of rabbit model of closed tibial fracture].

OBJECTIVE: To explore the effect of a modified three-point bending fracture device for establishing a rabbit model of closed tibial fracture. METHODS: The model of closed tibial fracture was established in 40 6-month-old male New Zealand white rabbits with a body weight of 2.5 to 3.0 kg, and the model was verified at 6 weeks after operation. Five rabbits underwent pre modeling without temporary external fixation before modeling, and then were fractured with a modified three-point bending fracture device;35 rabbits underwent formal modeling. Before modeling, needles were inserted, and splints were fixed externally, and then the fracture was performed with a modified three-point bending fracture device. The fracture model and healing process were evaluated by imaging and histopathology at 2 hours, 4 weeks, and 6 weeks after operation. RESULTS: Two hours after modeling, the prefabricated module showed oblique fracture in varying degrees and the broken end shifted significantly;Except for 1 comminuted fracture, 2 curved butterfly fractures and 2 without obvious fracture line, the rest were simple transverse and oblique fractures without obvious displacement in formal modeling group. According to the judgment criteria, the success rate of the model was 85.71%. Four weeks after modeling, the fixed needle and splint of the experimental rabbits were in good position, the fracture alignment was good, the fracture line was blurred, many continuous callus growths could be seen around the fracture end, and the callus density was high. Six weeks after modeling, many thick new bone trabeculae at the fracture, marginal osteoblasts attached, and a small number of macrophages were seen under the microscope. The intramembrane osteogenesis area was in the preparation bone stage, the medullary cavity at the fracture had been partially reopened, the callus was in the absorption plastic stage, and many osteoclasts were visible. The X-ray showed that the fracture line almost disappeared, part of the medullary cavity had been opened, the external callus was reduced around, the callus was in the plastic stage, and the bone cortex was continuous. It suggests that the fracture model showed secondary healing. CONCLUSION: The improved three-point bending fracture device can establish a stable rabbit model of closed tibial fracture, and the operation is simple, which meets the requirements of closed fracture model in basic research related to fracture healing.

Identification of priority pollutants and key factors affecting environmental risks of lead­zinc mine tailing sites.

Lead­zinc mine tailing sites are widely distributed in China. Tailing sites with different hydrological settings tend to have different susceptibilities toward pollution and hence different priority pollutants and environmental risks. This paper aims to identify priority pollutants and key factors influencing environmental risks of lead­zinc mine tailing sites with different types of hydrological settings. A database with detailed information on hydrological settings, pollution, etc. of 24 typical lead­zinc mine tailing sites in China was built. A rapid classification method of hydrological settings was proposed considering the groundwater recharge and migration of pollutants in the aquifer. Priority pollutants in leach liquor of tailings, soil, and groundwater of sites were identified using the osculating value method. The key factors affecting environmental risks of lead­zinc mine tailing sites were identified using the random forest algorithm. Four types of hydrological settings were classified. Pb/Zn/As/Cd/Sb, Fe/Pb/As/Co/Cd, and nitrate/iodide/As/Pb/Cd are identified as priority pollutants of leach liquor, soil, and groundwater, respectively. The lithology of the surface soil media, slope, and groundwater depth were identified as the top 3 key factors that affect the environmental risks of sites. Priority pollutants and key factors identified in this study can provide benchmarks for the risk management of lead­zinc mine tailing sites.

Microstructure and oxidation behavior of CoCrxCuFeMnNi high-entropy alloys fabricated by vacuum hot-pressing sintering.

Herein, CoCrxCuFeMnNi (x = 0, 0.5, 1.0, 1.5, and 2.0, in molar ratio) high-entropy alloys (HEAs) are fabricated by vacuum hot-pressing sintering (VHPS). The effect of Cr content on the microstructure and oxidation behavior are studied. When x ≤ 1.5 mol, the phases of the four alloys were all composed of FCC2 major phase and FCC1 secondary phase, while Cr2.0 alloy consisted of a small amount of FCC1 phase and ρ phase in addition to FCC2 main phase. The elemental segregation increased with the increase of Cr content. Cr2.0 alloy exhibited the lowest oxidation rate constants in the oxidation stage and the slow oxidation stage, which were 2.29 × 10-11 and 3.46 × 10-12 g2 cm-4 s-1, respectively, showing the best oxidation resistance. The oxidation products of CoCrxCuFeMnNi HEA system were mainly Mn4O3, Mn3O2, Cr2O3 and (M,Cr)3O4-type spinel oxides. The oxidation mechanism is mainly selective oxidation, that is, the outward diffusion of metal cations and the inward diffusion of oxygen ions. The oxidation resistance of the Cr-rich FCC1 and ρ phases is better than that of the copper-rich FCC2 phase.

The association between disruption of the circadian rhythm and aggravation of colitis in mice.

Delayed recovery from ulcerative colitis is mainly due to impaired healing of the intestinal epithelium after inflammation. The circadian rhythm controls cell proliferation and energy metabolism. However, the role of circadian genes in inflammatory bowel disease is largely unknown. The purpose of this study was to investigate whether disrupting the circadian rhythm in mice can worsen colitis by altering mitochondrial energy metabolism. Mice in the experimental groups were under physiologic stress with an 8-h light shift jet-lag schedule every 3 days, whereas those in the control group were not. Subsequently, half of the mice in the control and jet-lagged groups were given dextran sodium sulfate (DSS) to induce colitis. Mice in each group were euthanized at zeitgeber time (ZT)0, ZT4, ZT8, ZT12, ZT16, and ZT20. To investigate the effects of jet lag on the mice, colon specimens were subjected to hematoxylin and eosin staining to analyse mRNA and protein expression of core circadian clock genes (Bmal1, Clock, Per1, Per2, Cry1, Cry2, and Nr1d1). We analysed the mitochondrial morphology, adenosine triphosphate (ATP) levels, and the expression of dynamin-related protein 1 (Drp1) and ser637-phosphorylated (p)-Drp1, which are closely related to ATP production. We further investigated the effect of PER2 knock-down in the colon epithelial cells (CCD 841 CoN) by measuring ATP and cell proliferation levels. Disrupting the circadian rhythm changed the oscillation of clock genes in the colon of mice, altered the mitochondrial morphology of the colon specimens, decreased the expression of p-Drp1, reduced ATP production, and exacerbated inflammatory responses in mice with DSS-induced colitis. Additionally, silencing of PER2 in the colon epithelial cells reduced ATP production and cell proliferation. Disrupting the circadian rhythm in mice decreases mitochondrial energy metabolism in the colon and exacerbates symptoms of colitis.

[Effects of Precipitation Changes on Plant Community Diversity and Soil C:N:P Ecological Stoichiometric Characteristics in a Desert Steppe of China].

Studying the influence of precipitation patterns on plant community diversity, soil C:N:P ecological stoichiometric characteristics, and the relationships between key soil factors and plant community diversity is of great significance for the protection of plant community diversity in desert grasslands. This paper was studied in the desert steppe of the west of Loess Plateau using a three-year precipitation manipulation experiment (40% reduction in precipitation, 20% reduction in precipitation, natural precipitation, 20% increase in precipitation, and 40% increase in precipitation), explored the influence of changes in precipitation in dry and wet years on the diversity of plant community and soil C:N:P ecological stoichiometric characteristics. And we also explored the relationship between soil C:N:P ecological stoichiometric characteristics and the key soil factors and the diversity of plant community under changes in precipitation. The results showed that in a normal year and the drier year (2013 and 2015), Patrick richness and Shannon-Wiener diversity index were significantly low under the 20% reduction treatment compared with the control and 40% increase treatments, respectively. During the wetter year, Patrick richness and Shannon-Wiener diversity index were no different between any of the precipitation treatments. In the normal year and the drier year, the soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents and the carbon-nitrogen ratio (C:N), carbon-phosphorus ratio (C:P), and nitrogen-phosphorus ratio (N:P) all decreased with an increase in precipitation (the decrease in the C:N ratio was statistically significant). During the wetter year, SOC, TN, C:P, and N:P increased with an increase in precipitation. During the normal year, precipitation treatments had no significant influence on soil water content, having a limited influence on the plant community. TN, N:P, SOC, C:N, and microbial biomass nitrogen (MBN) had a more prominent influence on plant community diversity. In the wetter year, precipitation was abundant leading to a rise in soil nutrients. Water was not the most important factor limiting to plant growth whereas soil water content, soil nutrients, and ecological stoichiometric characteristics jointly regulate plant community diversity. In the drier years, precipitation treatments had a significant impact on soil water content, whereby an increase in precipitation led to high losses of soil nutrients. Therefore, soil water content was the most important factor affecting plant community diversity during drier years. These observations indicate that under dry and wet years, plant community diversity and soil C:N:P ecological stoichiometric characteristics have variable responses to precipitation and soil C:N:P effect on plant community were also different. These results provide a theoretical basis for the protection and management of desert steppe systems under future projected changes in precipitation.

[Influence of Precipitation Change on Soil Respiration in Desert Grassland].

Global climate change has significantly changed precipitation patterns. Soil respiration (SR), as an important pathway through which CO2 is released from the soil carbon pool into the atmosphere, may affect the carbon cycle process of terrestrial ecosystems and have a feedback effect on global climate change in response to precipitation change. However, at present there is limited understanding of how SR is affected by precipitation change. Field precipitation control experiments were conducted (with -40%, -20%, natural, 20%, and 40% precipitation) on desert grassland in the west of the Loess Plateau, to investigate the influence of precipitation change on SR dynamics and its relationship with soil water content, soil temperature, aboveground biomass, soil organic carbon, microbial biomass carbon, carbon-nitrogen ratio, and other factors. The results show that the diurnal variations of SR under different precipitation treatments were consistent in unimodal and bimodal models over three years. SR showed an increasing trend with added precipitation, relative to the control, and significant differences were observed between the second year (wetter) and the third year (drier) of the precipitation-manipulation experiment, indicating that precipitation changes had a legacy effect on SR. At the same time, SR was lowest under the -40% treatment and highest under the 40% treatment during the wetter year. The negative response of SR to precipitation exclusion treatments was stronger than the positive response to precipitation addition treatments. SR in drier years was significantly higher under precipitation addition treatments than the control, and the positive response of SR to increased precipitation treatment was significantly stronger than that under decreased precipitation treatment. In addition, soil water content, aboveground biomass, soil organic carbon, and carbon-nitrogen ratio were the environmental factors that obviously affected SR and increased with additional precipitation. SR increased with increases in soil water content, aboveground biomass, soil organic carbon, and carbon-nitrogen ratio, but decreased with increases in microbial biomass carbon. Among these factors, soil water content had the highest interpretation rate for SR, indicating that soil water content was the main environmental factor controlling SR in desert grassland. In both wetter and drier years, the amplitude of plant biomass input was lower than the amplitude of SR output under precipitation change, indicating that precipitation change may be unfavorable to soil carbon sequestration, especially in drier years, when precipitation change has a stronger influence on carbon pool output. Therefore, precipitation changes on SR in desert grassland in various dry and wet years may have different influences on the carbon cycle process of ecosystems, thus providing a reference for regional carbon budget assessment.

[Responses of plant growth of different life-forms to precipitation changes in desert steppe]. / è’æ¼ è‰åŽŸåŒºä¸åŒç”Ÿæ´»åž‹æ¤ç‰©ç”Ÿé•¿å¯¹é™æ°´å˜åŒ–çš„å“åº”.

Under the background of global climate change, precipitation changes will have profound impacts on plant community dynamics. Through field experiment with precipitation manipulation in a desert steppe of western Loess Plateau, we examined the responses of species richness, density, coverage, height and aboveground biomass of different plant life-forms to precipitation changes. The results showed significant effects of precipitation on richness, density and coverage of annual herbs in the third year of manipulation experiment (2015), with lowest values in the decreased precipitation treatments. The height of annual herbs was more sensitive to precipitation changes, and was lowest in the -40% precipitation treatment during three years. The magnitudes of negative response of growth and aboveground biomass of annual herbs to decreased precipitation were larger than that to increased precipitation. Richness, density and coverage of perennial herbs in the decreased precipitation were significantly lower than those in the +40% precipitation in the 3rd year, but were insignificantly different from the control. The height of perennial herbs was lowest in the -40% precipitation treatment during three years. The magnitudes of negative response of richness, coverage and height of perennial herbs to decreased precipitation were larger than positive response to increased precipitation, while the positive response of aboveground biomass to the +40% precipitation treatment was stronger. The positive responses of richness, density, coverage and aboveground biomass of shrub to ±20% precipitation treatments were most obvious, which might be related to the relatively concentrated distribution of shrub in these treatments. The precipitation reduction inhibited the growth of herbaceous plants, particularly on the annual herbs, whereas increasing precipitation promoted perennial herbaceous growth and biomass accumulation to some extent. The annual herbaceous growth and biomass fluctuated with interannual variation of precipitation. Shrubs were relatively less affected by precipitation changes. Precipitation changes would have significant effects on plant community composition and function of desert steppe in western Loess Plateau.

[Process of land use transition and its impact on regional ecological quality in the Middle Reaches of Heihe River, China]. / é»‘æ²³ä¸­æ¸¸åœŸåœ°åˆ©ç”¨è½¬åž‹è¿‡ç¨‹åŠå ¶å¯¹åŒºåŸŸç”Ÿæ€è´¨é‡çš„å½±å“.

Land use transition is one of the main drivers of regional ecosystem change in arid area, which directly affects human well-being. Based on the satellite images of 1987, 2001 and 2016, the change detection assessment model and ecological response model were used to analyze the process of land use transition and response of ecological quality during 1987-2016 in the ecologically fragile middle reaches of the Heihe River. The results showed that the land use change was significant during 1987-2016 and the total change increased significantly, as well as the continuous increase of the cultivated land and construction land. There was a strong tendency of transform from grassland to cultivated land, while the tendency of transforming unused land to other land classes was not strong under a random process of gain or loss. During 1987-2016, the ecological quality of the study area displayed a decreasing trend as a whole and the ecological land decreased by 2.8%. The land use transition with the greatest impact on the ecological environment degradation was the transition of the grassland to the cultivated land and unused land. Therefore, in order to promote the sustainable use of regional land resources and to improve the regional ecological quality, it is necessary to allocate the proportion of production land and ecological land according to the regional water resources.

[Relationships of wetland landscape fragmentation with climate change in middle reaches of Heihe River, China].

Based on the 1975-2010 multi-temporal remotely sensed TM and ETM images and meteorological data, in combining with wavelet analysis, trend surface simulation, and interpolation method, this paper analyzed the meteorological elements' spatial distribution and change characteristics in the middle reaches of Heihe River, and elucidated the process of wetland landscape fragmentation in the study area by using the landscape indices patch density (PD), mean patch size (MPS), and patch shape fragment index (FS). The relationships between the wetland landscape fragmentation and climate change were also approached through correlation analysis and multiple stepwise regression analysis. In 1975-2010, the overall distribution patterns of precipitation and temperature in the study area were low precipitation in high temperature regions and high precipitation in low temperature regions, and the main characteristics of climate change were the conversion from dry to wet and from cold to warm. In the whole study period, the wetland landscape fragmentation was mainly manifested in the decrease of MPS, with a decrement of 48.95 hm2, and the increase of PD, with an increment of 0.006 ind x hm(-2).