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Sublethal or not? Responses of multiple biomarkers in Daphnia magna to single and joint effects of BDE-47 and BDE-209
No full textPolybrominated diphenyl ethers (PBDEs) are extremely incessant anthropogenic contaminants found in the environment, with dreadful risk to aquatic ecosystems. However, there is a limited amount of data concerning their impacts on freshwater organisms. 2,2',3,3',4,4',5,5',6,6'-decabromodiphenyl ether (BDE-209) and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) are significant components of total PBDEs in water. The sublethal effects of BDE-47, BDE-209 and their binary mixtures on the aquatic organism Daphnia magna were investigated in acute and chronic exposure experiments. Immobilization and heartbeat were studied in daphnids after 48 h of exposure. Mortality rate, breed number, Cholinesterase (ChE), Glutathione S-transferases (GST) and Catalase (CAT) activities were evaluated after 21 days of exposure. The results showed that at 100 and 200 mu g/L concentration of BDE-47, immobilization rate of daphnids were inhibited by 44.0 +/- 16.7% and 88.0 +/- 10.9%, respectively. The binary mixture of BDE-47 and BDE-209 had uncongenial effects on immobilization of D. magna under acute toxicity test. BDE-209 significantly increased the heartbeat rate of daphnids, which increased even further when combined with BDE-47. After 21 days of exposure, daphnids exposed to single BDE-47 were physiologically altered. The combination of BDE-47 with BDE-209 significantly decreased the mortality rate of daphnids. Irrespective of the concentration, higher numbers of offsprings were produced in the mixtures compared to BDE-47 treatment alone. ChE activities significantly (p < 0.05) decreased at concentrations of 2 and 4 pg/L in single BDE-47 treatment, while GST activity significantly (p < 0.05) decreased at 0.5 g/L. CAT activities significantly increased with BDE-47 treatments in all the tested concentrations (p < 0.05). The mixtures significantly affect ChE (p < 0.05), GST (p < 0.05) and CAT activities (p < 0.05). The results illustrated that the toxicity of the mixture of PBDE congeners exposed to aquatic organisms may have antagonistic effects. The 21 days chronic test in this study suggests that acute toxicity tests, i.e. 48-h tests, using Daphnia may lead to underestimation of risks associated with PBDEs, especially, BDE-209. Hence, there is a necessity to re-examine PBDE congeners' environmental risk in aquatic organisms
A general and simple method for evaluating the electrical transport performance of graphene by the van der Pauw-Hall measurement
No full textExpected for many promising applications in the field of electronics and optoelectronics, a reliable method for the characterization of graphene electrical transport properties is desired to predict its device performance or provide feedback for its synthesis. However, the commonly used methods of extracting carrier mobility from graphene field effect transistor or Hall-bar is time consuming, expensive, and significantly affected by the device fabrication process other than graphene itself. Here we reported a general and simple method to evaluate the electrical transport performance of graphene by the van der Pauw-Hall measurement. By annealing graphene in vacuum to remove the adsorbed dopants and then exposing it in ambient surroundings, carrier mobility as a function of density can be measured with the increase of carrier density due to the dopant re-adsorption from the surroundings. Further, the relationship between the carrier mobility and density can be simply fitted with a power equation to the first level approximation, with which any pair of measured carrier mobility and density can be normalized to an arbitrary carrier density for comparison. We experimentally demonstrated the reliability of the method, which is much simpler than making devices and may promote the standard making for graphene characterization. (C) 2018 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved
Winter plant phenology in the alpine meadow on the eastern Qinghai-Tibetan Plateau
No full textThere is no knowledge of winter plant phenology and its controlling factors on the Qinghai-Tibetan Plateau (QTP). Thus, we conducted a 4 year winter phenology and growth dynamics study in the alpine meadow on the eastern QTP. From November 2013 to March 2017, the phenology of the 'winter-growth' and 'winter-green' species was recorded every 5 d. In November-February from 2014 to 2015, the above-ground biomass (AGB) in random plots was calculated to distinguish different growth patterns among winter growing species. The percentage of winter abundance relative to the summer population for forbs and the percentage of absolute coverage for grasses (W/S) were calculated to describe the importance of the winter population to the summer population. The soil moisture (SM) and soil temperature (ST) were used to explore the controlling factors on the AGB. Pearson's correlation analysis between winter phenology data and environmental variables, including air temperature (T-air), snow cover fraction (SCF), SM and ST, was used to investigate the factors affecting winter phenology during November-February from 2014 to 2017. There were 107 species in total in the sites, including ten 'winter-growth' species and four 'winter-green' species. Among the 'winter-green' species, Festuca ovina and Deschampsia cespitosa were the dominant species in the sites. The 'winter-growth' species grew new leaves or ramets or transitioned to reproductive growth. Gentiana spathulifolia even flowered in winter. 'Winter-growth' made important contributions to the annual AGB, e.g. winter growth of G. spathulifolia accounted for 23.26 % of its annual AGB, while 14.74 % of the annual AGB of G. crassuloides was from winter growth. In addition, winter warming and snowfall reduction under global climate change on the eastern QTP may decrease the AGB increment of the 'winter-growth' and delay the green-up onset date of 'winter-green' species. Also, winter warming and snowfall reduction may advance the first flowering date of 'winter-growth' species. In contrast to previous views that plants on the QTP were generally considered to remain dormant in winter, our study revealed that alpine meadow plants had strong winter growth which suggested the importance of re-evaluating the dynamics of ecosystem function of alpine meadow, including its contribution to the global carbon balance. It was also shown that soil moisture availability is more important than warmer temperature in controlling the green-up onset of 'winter-green' species on the eastern QTP, which contrasts with the traditional view that warmer winters could advance green-up. As snowmelt is the only source of soil water in winter, the prediction of the green-up trend may be further complicated by snowfall variation in winter
Premnafulvol A: A Diterpenoid with a 6/5/7/3-Fused Tetracyclic Core and Its Biosynthetically Related Analogues from Premna fulva
No full textPremnafulvol A (1), a unique diterpenoid featuring a 6/5/7/3-fused tetracyclic carbon skeleton, with three biosynthetically related analogues, premnafulvols B-D (2-4), were isolated from the aerial parts of Premna fulva. Structures of 1-4 were established by a combination of extensive spectroscopic analyses, quantum chemical calculations, and X-ray crystallography. Plausible biosynthetic pathways of 1-4 were proposed. Interestingly, 2 and 3 exhibited opposite effects on estrogen biosynthesis in human ovarian granulosa-like KGN cells by modulating the expression of aromatase
A new species of the odorous frog genus Odorrana (Amphibia, Anura, Ranidae ) from southwestern China
No full textThe genus Odorrana is widely distributed in the mountains of East and Southeastern Asia. An increasing number of new species in the genus have been recognized especially in the last decade. Phylogenetic studies of the O. schmackeri species complex with wide distributional range also revealed several cryptic species. Here, we describe a new species in the species complex from Guizhou Province of China. Phylogenetic analyses based on mitochondrial DNA indicated the new species as a monophyly clustered into the Odorrana Glade and sister to O. schmackeri, and nuclear DNA also indicated it as an independent lineage separated from its related species. Morphologically, the new species can be distinguished from its congeners based on a combination of the following characters: (1) having smaller body size in males (snout-vent length (SVL) <43.3 mm); (2) head longer than wide; (3) dorsolateral folds absent; (4) tympanum of males large and distinct, tympanum diameter twice as long as width of distal phalanx of finger III; (5) two metacarpal tubercles; (6) relative finger lengths: II < I < IV < III; (7) tibiotarsal articulation reaching to the level between eye to nostril when leg stretched forward; (8) disks on digits with circum-marginal grooves; (9) toes fully webbed to disks; (10) the first subarticular tubercle on fingers weak; (11) having white pectoral spinules, paired subgular vocal sacs located at corners of throat, light yellow nuptial pad on the first finger in males
Divergence of Fecal Microbiota and Their Associations With Host Phylogeny in Cervinae
No full textGastrointestinal microbiota may shape the adaptation of their hosts to different habitats and lifestyles, thereby driving their evolutionary diversification. It remains unknown if gastrointestinal microbiota diverge in congruence with the phylogenetic relationships of their hosts. To evaluate the phylosymbiotic relationships, here we analyzed the compositions of fecal microbiota of seven Cervinae species raised in the Chengdu Zoo. All sampled animals were kept in the same environmental condition and fed identical fodder for years. Results showed that Firmicutes and Bacteroidetes were dominant in their fecal microbiota. Even though some bacteria (e.g., Ruminococcaceae) were found to be common in the feces of all investigated species, some genera (e.g., Sharpea and Succinivibrio) were only observed in animals with particular digestive systems. As for the intraspecies variations of microbial communities, only a few operational taxonomic units (OTUs) were shared among replicates of the same host species although they accounted for most of the total abundance. Correlation was observed between the fecal microbiota divergence and host phylogeny, but they were not congruent completely. This may shed new light on the coevolution of host species and their microbiota
Enantioselective synthesis of gem-diarylalkanes by transition metal-catalyzed asymmetric arylations (TMCAAr)
No full textChiral gem(1,1)-diaryl containing tertiary or quaternary stereogenic centers are present in many natural products and important pharmacophores. While numerous catalytic asymmetric methods enable access to 1,1-diaryl motifs, transition metal-catalyzed asymmetric arylations (TMCAAr) are one of the most powerful methods to prepare enantiopure gem-diarylalkane compounds. The main methodology includes enantioselective 1,2- or 1,4-additions across C=O, C=N and C=C bonds by arylmetallic reagents; aryl cross-couplings of olefins, benzylic (pseudo) halides and aziridines; asymmetric aryl substitution reactions of allylic substrates; and isotopic benzylic C-H arylation
Application of analytic hierarchy process in wetland degradation research
No full text若尔盖高原沼泽湿地是我国面积最大的高寒沼泽湿地,在涵养水源、调节气候等方面具有十分重要的生态功能.采用Arcgis版本,分别从1978、1990、2000和2008年的中国湿地分布图中提取出若尔盖高原的湿地分布图,分析4个时期湿地的面积变化.发现若尔盖高原湿地面积由1978年的6 170 km~2下降至2008年的5 379 km~2,整体变化幅度为-12.83%,变化率为-0.43%.通过层次分析法分析若尔盖高原湿地面积减少的驱动因子,发现导致湿地面积减少的主要因子是超载过牧、挖沟排水、降雨变化、鼠虫害、人口增长,其权重值分别为0.380 1、0.157 3、0.138 6、0.075 2、0.073 3.上述结果表明若尔盖高原湿地在过去30年呈退化趋势,而导致湿地退化的原因是自然因素和人类活动的共同作用
Identification and differential regulation o microRNAs during thyroid hormone-dependent metamorphosis in Microhyla fissipes
No full textBackground: Anuran metamorphosis, which is obligatorily initiated and sustained by thyroid hormone (TH), is a dramatic example of extensive morphological, biochemical and cellular changes occurring during post-embryonic development Thus, it provides an ideal model to understand the actions of the hormone and molecular mechanisms underlying these developmental and apoptotic processes. In addition to transcriptional factors, microRNAs (miRNAs) play key roles in diverse biological processes via post-transcriptional repression of mRNAs. However, the possible role of miRNAs in anuran metamorphosis is not well understood. Screening and identification of TH-responding miRNAs are required to reveal the integrated regulatory mechanisms of TH during metamorphosis. Given the specific role of TRs during M. fissipes metamorphosis and the characteristics of M. fissipes as an ideal model, Illumina sequencing technology was employed to get a full scope of miRNA in M. fissipes metamorphosis treated by T3. Results: Morphological and histological analysis revealed that 24 h T3 treatment M. fissipes tadpoles resembled that at the climax of natural metamorphosis. Thus, small RNA libraries were constructed from control and 24 h T3 treatment groups. A total of 164 conserved miRNAs and 36 predicted novel miRNAs were characterized. Furthermore, 5' first and ninth nucleotides of miRNAs were significantly enriched in U in our study. In all, 21 miRNAs were differentially expressed between the T3 and control groups (p < 0.01). A total of 10,206 unigenes were identified as target genes of these differentially expressed miRNAs. KEGG pathway analysis indicated that the most overrepresented miRNA target genes were enriched in the "PI3k-Akt signaling pathway". In addition, a network associated with the TH signaling pathway provides an opportunity to further understand the complex biological processes that occur in metamorphosis. Conclusions: We identified a large number of miRNAs during M. fissipes metamorphosis, and 21 of them were differentially expressed in the two groups that represented two different metamorphic stages. These miRNAs may play important roles during metamorphosis. The study gives us clues for further studies of the mechanisms of anuran metamorphosis and provides a model to study the mechanism of TH-affected biological processes in humans
Metal coordination protocol for the synthesis of-2,3-dehydrosilybin and 19-O-demethy1-2,3-dehydrosilybin from silybin and their antitumor activities
No full textAn efficient and practical method to access bioactive 2,3-dehydrosilybin and 19-O-demethy1-2,3-dehydrosilybin using naturally abundant flavonolignan silybin in the presence of metal salt as a chelating agent is described. The procedure presented here has several advantages including one-pot, synthetic ease, and products in high yields with no side reactions, and large-scale feasibility. The dehydrogenation and demethylation proceed smoothly via a one-pot process using the AlCl3/Pyridine system and 12 as the additive. Furthermore, 2,3-dehydrosilybin and 19-O-demethy1-2,3-dehydrosilybin can inhibit the expression of intracellular mature miRNA-21 with IC50 values of 4.46 mu M and 8.25 mu M, respectively, and show moderate anticancer activities against HeLa cell lines. (C) 2018 Elsevier Ltd. All rights reserved