Transplantation of fibrin-thrombin encapsulated human induced neural stem cells promotes functional recovery of spinal cord injury rats through modulation of the microenvironment

Recent studies have mostly focused on engraftment of cells at the lesioned spinal cord,with the expectation that differentiated neurons facilitate recovery.Only a few studies have attempted to use transplanted cells and/or biomaterials as major modulators of the spinal cord injury microenvironment.Here,we aimed to investigate the role of microenvironment modulation by cell graft on functional recovery after spinal cord injury.Induced neural stem cells reprogrammed from human peripheral blood mononuclear cells,and/or thrombin plus fibrinogen,were transplanted into the lesion site of an immunosuppressed rat spinal cord injury model.Basso,Beattie and Bresnahan score,electrophysiological function,and immunofluorescence/histological analyses showed that transplantation facilitates motor and electrophysiological function,reduces lesion volume,and promotes axonal neurofilament expression at the lesion core.Examination of the graft and niche components revealed that although the graft only survived for a relatively short period(up to 15 days),it still had a crucial impact on the microenvironment.Altogether,induced neural stem cells and human fibrin reduced the number of infiltrated immune cells,biased microglia towards a regenerative M2 phenotype,and changed the cytokine expression profile at the lesion site.Graft-induced changes of the microenvironment during the acute and subacute stages might have disrupted the inflammatory cascade chain reactions,which may have exerted a long-term impact on the functional recovery of spinal cord injury rats.

Responses of nutrient biogeochemistry and nitrogen cycle to seasonal upwelling in coastal waters of the eastern Hainan Island

The coastal upwelling has profound influence on the surrounding ecosystem by supplying the nutrient-replete water to the euphotic zone.Nutrient biogeochemistry was investigated in coastal waters of the eastern Hainan Island in summer 2015 and autumn 2016.From perspectives of nutrient dynamics and physical transport,the nutrient fluxes entered the upper 50 m water depth(between the mixed layer and the euphotic zone)arisen from the upwelling were estimated to be 2.5-5.4 mmol/(m^(2)·d),0.15-0.28 mmol/(m^(2)·d),and 2.2-7.2 mmol/(m^(2)·d)for dissolved inorganic nitrogen(DIN),phosphate(DIP),and dissolved silicate(DSi),respectively,which were around 6-to 12-fold those in the background area.The upwelled nutrients supported an additional plankton growth of(14.70±8.95)mg/m^(2)for chlorophyll a(Chl a).The distributions of nitrateδ^(15)N andδ^(18)O above the 300 m water depth(top of the North Pacific Intermediate Water)were different among the upwelling area,background area in summer,and the stations in autumn,and the difference of environmental and biogeochemical conditions between seasons should be the reason.The higher DIN/DIP concentration ratio,nitrate concentration anomaly,and lower nitrate isotope anomaly(Δ(15,18))in the upper ocean in summer than in autumn indicated the stronger nitrogen fixation and atmospheric deposition,and the following fixed nitrogen regeneration in summer.The higher values of Chl a and nitrateδ^(15)N andδ^(18)O within the euphotic zone in autumn than the background area in summer suggested the stronger nitrate assimilation in autumn.The differences in relatively strength of the assimilation,nitrogen fixation and atmospheric deposition,and the following remineralization and nitrification between the two seasons made the higherδ^(18)O:δ^(15)N and larger difference of enzymatic isotope fractionation factors^(15)εand^(18)εfor nitrate assimilation in summer than in autumn above the North Pacific Tropical Water.

Using triple oxygen isotopes and oxygen-argon ratio to quantify ecosystem production in the mixed layer of northern South China Sea slope region

Quantifying the gross and net production is an essential component of carbon cycling and marine ecosystem studies.Triple oxygen isotope measurements and the O_(2)/Ar ratio are powerful indices in quantifying the gross primary production and net community production of the mixed layer zone,respectively.Although there is a substantial advantage in refining the gas exchange term and water column vertical mixing calibration,application of mixed layer depth history to the gas exchange term and its contribution to reducing indices error are unclear.Therefore,two cruises were conducted in the slope regions of the northern South China Sea in October 2014(autumn)and June 2015(spring).Discrete water samples at Station L07 in the upper 150 m depth were collected for the determination ofδ^(17)0,δ^(18)O,and the O_(2)/Ar ratio of dissolved gases.Gross oxygen production(GOP)was estimated using the triple oxygen isotopes of the dissolved O_(2),and net oxygen production(NOP)was calculated using O_(2)/Ar ratio and O_(2)concentration.The vertical mixing effect in NOP was calibrated via a N_(2)O based approach.GOP for autumn and spring was(169±23)mmol/(m^(2)·d)(by O_(2))and(189±26)mmol/(m^(2)·d)(by O_(2)),respectively.While NOP was 1.5 mmol/(m^(2)·d)(by O_(2))in autumn and 8.2 mmol/(m^(2)·d)(by O_(2))in spring.Application of mixed layer depth history in the gas flux parametrization reduced up to 9.5%error in the GOP and NOP estimations.A comparison with an independent O_(2)budget calculation in the diel observation indicated a26%overestimation in the current GOP,likely due to the vertical mixing effect.Both GOP and NOP in June were higher than those in October.Potential explanations for this include the occurrence of an eddy process in June,which may have exerted a submesoscale upwelling at the sampling station,and also the markedly higher terrestrial impact in June.

A Method for Elastic Shear Buckling Calculation of Curved Bridge Webs

Curved composite bridges and curved steel bridges have already been constructed around the world;however, the calculation for shear buckling of curved bridge webs generally uses the equations for straight bridge webs or just introduces a modification factor for bridge design. In this paper, the curved bridge web is equivalent to an isotropic cylindrical flat shell, and the double triangular series satisfying four-edge simply supported boundaries are used as the displacement function of the shell. Then by means of the Galerkin method, the analytical formula for elastic shear buckling stress of curved bridge webs is deduced. The parameter studies show that the shear buckling coefficient kc of curved bridge webs is positively correlated with the parameter h2 / (Rt), and negatively correlated with the length-height ratio l/ h. This implies that the elastic shear buckling stress of a curved bridge web is larger than that of an equivalent straight bridge web. For a curved bridge with the parameter h2 / (Rt) less than 2, the amount of increase is less than 4.5%. The elastic shear buckling stress of curved bridge webs can be estimated conservatively as the webs in straight bridges. While for a curved bridge with larger h2 / (Rt), using the equations for straight girders to calculate the elastic shear buckling stress is too conservative. The proposed formulas provide a more accurate estimation for shear buckling stress of curved bridge webs.

长江口外低氧区及其邻近海域表层沉积物反硝化微生物多样性和分布特征

【目的】微生物参与的反硝化是河口区氮损失的主要途径。【方法】本研究采用Illumina MiSeq测序方法,研究了长江口外低氧区及其邻近海域表层沉积物中nirS型和nirK型反硝化微生物群落的多样性和分布特征。【结果】样品共检测到346个nirS Operational Taxonomic Units和267个nirK Operational TaxonomicUnits,根据采样地的环境特征及nirS型和nirK型反硝化微生物群落聚类分析结果将所有OperationalTaxonomicUnits划分为低氧区、南部区域及外部深水区,其中外部深水区的样品nirS功能基因的多样性最高。各实验样地优势Operational Taxonomic Units在系统进化关系上可分为多个不同的簇。此次发现的所有优势OperationalTaxonomicUnits均属于未被培养的菌群,其中部分Operational Taxonomic Units还是首次被发现。此外还发现nirS功能基因对低氧区的环境适应性更好。【结论】我们的研究结果表明广泛存在的反硝化微生物在河口沉积物的氮循环中发挥重要作用。

Lineage tracing reveals the origin of Nestin-positive cells are heterogeneous and rarely from ependymal cells after spinal cord injury

Nestin is expressed extensively in neural stem/progenitor cells during neural development, but its expression is mainly restricted to the ependymal cells in the adult spinal cord. After spinal cord injury(SCI), Nestin expression is reactivated and Nestinpositive(Nestin;) cells aggregate at the injury site. However, the derivation of Nestin;cells is not clearly defined. Here, we found that Nestin expression was substantially increased in the lesion edge and lesion core after SCI. Using a tamoxifen inducible CreER(T2)-loxP system, we verified that ependymal cells contribute few Nestin;cells either to the lesion core or the lesion edge after SCI. In the lesion edge, GFAP+astrocytes were the main cell type that expressed Nestin;they then formed an astrocyte scar.In the lesion core, Nestin;cells expressed αSMA or Desmin, indicating that they might be derived from pericytes. Our results reveal that Nestin;cells in the lesion core and edge came from various cell types and rarely from ependymal cells after complete transected SCI, which may provide new insights into SCI repair.

From the water sources of the Tibetan Plateau to the ocean:State of nutrients in the Changjiang linked to land use changes and climate variability

Anthropogenic activity is an important driver of changes in the chemistry of nutrients(N,P,and Si)over watersheds at the sub-continental scale(e.g.,106km~2)and can markedly modify their seaward fluxes to the global ocean.In the present study,we reviewed the current status of nutrient chemistry in Changjiang(Yangtze River)based on data collected through 11 expeditions along a river course spanning 4,500 km and 15–20 major tributaries during 1997–2016 as well as monthly monitoring at the river mouth since 1980.The data were analyzed together with published results in the literature to synthesize the recent developments and current state of nutrients in the Changjiang.Previously published results from the Qinghai-Tibetan Plateau head waters were included to realize the systematics of nutrients for the whole drainage basin.Here,we showed that tributaries of the upper reaches of watersheds collectively determine the regime with high concentration and skewed species ratio of nutrients in the Changjiang mainstream,producing profound effects over a water course of 2,000–2,500 km further downstream and until the river mouth.Moreover,using data across the Three Gorges Reservoir(TGR)during 2003–2016,we evaluated the trapping and/or amplifying effects of the Three Gorges Dam(TGD)on nutrient chemistry.Tide-influenced river delta contributed an additional 20%dissolved inorganic phosphorus and 5–10%dissolved inorganic nitrogen and dissolved silicates to the seaward flux,dramatically affecting the stoichiometry of nutrients at the river mouth.Next,based on compiled data on supply and export,legacy nutrients were evaluated.Both nitrogen and phosphorus are in the accumulation phase over the watersheds,and the legacy nutrient fluxes are much higher than the annual riverine seaward fluxes.Finally,we demonstrated that the seaward fluxes of anthropogenic nutrients from the Changjiang exceed those from other top 10 largest rivers on this planet,which can be attributed to land use changes in the China over the last three to four decades.