天山高寒草原土壤团聚体结构与养分含量对模拟氮磷沉降的响应

为更好地理解高寒草原土壤团聚体结构及其养分含量对氮(N)、磷(P)沉降增加的响应,于2018年开始依托全球营养网络(Nutrient Network)在巴音布鲁克草原生态系统研究站开展模拟氮磷沉降的短期(<5年)氮磷添加控制实验,设置对照(CK)、N添加、P添加、NP交互添加4个处理。N、P添加量均为10 g m^-2 a^-1。于2021年8月采集植物与土壤样品,采用湿筛法分析土壤水稳定性团聚体组成,测定全土和各粒级团聚体有机碳(SOC)、总氮(TN)、总磷(TP)、速效氮(AN)和速效磷(AP)含量。研究结果表明：(1)巴音布鲁克高寒草原各粒级土壤团聚体比例从低到高依次为：0.053—0.25 mm、<0.053 mm、0.25—2 mm、和>2 mm,以>2 mm团聚体占主导,其比例在45.48%—71.81%之间。(2)N添加显著降低了0—10 cm土壤层>2 mm团聚体比例和团聚体稳定性,而P添加则显著降低了10—20 cm土壤层>2 mm团聚体比例和团聚体稳定性。(3)0—10 cm土壤层各粒级团聚...     

Influence of parathyroid status of rats on renal tubular handling of adenosine 3'5'-monophosphate: a micropuncture study

In order to correlate cyclic AMP handling by the nephron to the parathyroid status, clearance and micropuncture experiments were performed in rats with intact parathyroid glands, or immediately after parathyroidectomy, or six days after parathyroidectomy. In intact animals cyclic AMP urinary excretion was about twice the filtered load and the tubular addition of the nucleotide was achieved at the end of the accessible proximal tubule. In acutely parathyroidectomized rats cyclic AMP urinary excretion was not different from the filtered load and no proximal tubular addition was detected at the late accessible proximal tubule. In chronically parathyroidectomized animals urinary excretion of cyclic AMP was not different from the filtered load, nevertheless a proximal tubular addition of the nucleotide was observed, similar in magnitude to that of intact rats. The data afford a direct evidence that the convoluted proximal tubule is the major site of cyclic AMP tubular addition, confirm that this addition disappears immediately after parathyroidectomy, but indicate that it re-occurs in chronic parathyroidectomy.     

氮水添加对放牧背景下荒漠草原生产力的影响

水分与氮素作为干旱和半干旱草原生产力的共同限制性因子在退化草原的生态快速修复过程中备受关注。以不同放牧强度背景下的短花针茅荒漠草原为研究对象,开展围封模拟放牧利用实验,同时添加氮素和水分。通过分析历史放牧强度与年份对生产力的影响,以及添加氮素和水分对不同功能群植物生物量的作用,探讨放牧强度对短花针茅草原生产力的内在作用机制,以及如何实现荒漠草原资源合理开发和可持续利用。研究结果显示,降雨量与放牧强度决定着短花针茅草原的植物群落结构。氮素和水分添加可分别提升11%-29%和12%-32%的群落地上生物量,且二者存在显著的交互作用。不同功能群植物的地上生物量对氮素与水分添加的响应存在差异,多年生丛生禾草对氮素和水分添加响应最敏感。氮素与水分添加可显著提高多年生丛生禾草的地上生物量,但与自然降水量相关。氮素添加对地上生物量的影响在正常降雨和稍旱年份作用显著,而水分添加在干旱年份作用显著。在正常降雨年份,以半灌木植物为优势种的轻度放牧背景以添加水分对提升生产力最宜,以多年生丛生禾草和半灌木为共优种的中度放牧背景和以多年生丛生禾草为优势种的重度放牧以同时添加水分和氮素对提升生产力最为宜;在干旱年份不同放牧强度背景下均以同时添加水分和氮素对提升生产力最为宜。我们的结果表明了养分与资源的改善有利于退化短花针茅草原的快速恢复和可持续生产。     

矿区分离丛枝菌根真菌对万寿菊吸Cd潜力影响

盆栽试验研究土壤不同施Cd水平(0、5、20、50μg/g)下,接种矿区污染土壤中丛枝菌根真菌对万寿菊根系侵染率、植株生物量及Cd吸收与分配的影响。结果表明:接种丛枝菌根真菌显著提高Cd胁迫下万寿菊的根系侵染率和植株生物量;随着施Cd水平提高,各处理植株Cd浓度显著增加。各施Cd水平下万寿菊地上部Cd吸收量远远高于根系Cd吸收量,在土壤施Cd量达到50μg/g时,接种处理地上部Cd吸收量是根系的3.48倍,对照处理地上部Cd吸收量是根系的1.67倍;同一施Cd水平下接种处理植株Cd吸收量要显著高于对照。总体上,试验条件下污染土壤中分离的丛枝菌根真菌促进了万寿菊对土壤中Cd的吸收,并在一定程度上增加Cd向地上部分的运转,表现出植物提取的应用潜力。     

热带次生林不同林层植物叶片非结构性碳水化合物的季节变化及其对氮磷添加的响应

非结构性碳水化合物(Non-structural Carbohydrates, NSCs)是植物生长代谢过程中重要的能量来源。通过在华南热带次生林进行氮磷添加试验,探究不同林层植物叶片NSCs的季节变化及其对氮磷添加的响应,取样时间为2019年1月、4月、7月和10月。结果表明:1)植物叶片NSCs存在显著的种间差异,磷(P)添加对叶片淀粉和NSCs含量具有显著影响,且物种与磷添加的交互作用显著影响叶片淀粉含量。2)黑嘴蒲桃和紫玉盘叶片NSCs含量对氮(N)添加的响应较为敏感,而白车和竹节叶片NSCs含量对P添加的响应较为敏感,氮磷同时添加(+NP)对植物叶片NSCs的增效作用最好。3)植物叶片NSCs存在显著的季节性变化,且季节与林层间的交互作用对叶片可溶性糖和NSCs含量具有显著影响。4)不同林层植物对氮磷添加的响应不同,氮磷添加使林下层植物叶片可溶性糖含量增高,林冠层降低,在干季,N添加会使林下层植物叶片淀粉含量增高,林冠层降低。P添加的影响恰好与之相反。在湿季,氮磷添加使林下层和林冠层植物叶片的淀粉含量增加。5)林冠层植物叶片NSCs含量高于林下层,且林下层植物叶片NSCs含量...     

Addition of Novobiocin in pre-enrichment step can improve Salmonella culture protocol of modified semisolid Rappaport-Vassiliadis

The aim was to investigate the effect of addition of Novobiocin to the non-selective buffered peptone water (BPW) for pre-enrichment of Salmonella in connection with plating on modified semisolid Rappaport-Vassiliadis (MSRV). In a semi-quantitative study, the level of Salmonella following pre-enrichment of 32 presumably naturally contaminated swine fecal samples were assessed for BPW with and without addition of Novobiocin (22 microg/ml). In another experiment, a total of 400 swine fecal samples were screened for the presence of Salmonella spp., in order to compare the performance of the non-selective pre-enrichment broth with BPW made semi-selective by addition of Novobiocin. The semi-quantitative assessment of the Salmonella level showed that addition of Novobiocin in the pre-enrichment step on average increased the level of Salmonella 1.2 log dilution steps. When growth was scored at five levels, 90 samples opposed to 50 yielded a strong positive reading (+++) when Novobiocin was applied. Growth was on average 0.3 scores higher when pre-enriched with Novobiocin. The difference in growth score medians of the two methods was highly significant (Sign test; p<0.001). Despite the increased sensitivity, 13 culture-positive samples were missed when using the Novobiocin-containing BPW. In conclusion, a simple addition of Novobiocin in the BPW pre-enrichment step of fecal samples may facilitate reading and thereby detection of Salmonella on MSRV. The increase of Salmonella in the semi-quantitative study may be caused by a reduction in the number of competitive microorganisms.     

Galactosamine decreases nitric oxide formation in cultured rat hepatocytes: mechanism of suppression

We have shown that nitric oxide production is dramatically decreased in rat primary hepatocyte cultures exposed to galactosamine. Cotreatment of the cells with uridine, which is known to prevent cytotoxicity, was found to also attenuate NO loss. In the present study, two possible mechanisms for the decreased nitric oxide production were examined. First, we examined the possibility that galactosamine could interfere with the uptake of extracellular arginine by the cultured hepatocytes. Cellular uptake of arginine was determined after addition of 14C-arginine at the time of hepatocyte attachment. Uptake of arginine was rapid in control cultures, and both the rate and level of uptake were unchanged by the addition of a cytotoxic concentration of galactosamine (4 mM). In addition, increased concentrations of arginine in the cell culture medium did not ameliorate the galactosamine-induced decrease in production of nitric oxide. Second, we determined whether the synthesis of inducible nitric oxide synthase in the hepatocyte cultures was inhibited by addition of galactosamine. Hepatocyte levels of inducible nitric oxide synthase were determined immunochemically at various times after the addition of galactosamine (4 mM). In control cultures, inducible nitric oxide synthase was detectable at 7 and 24 hours after attachment. In contrast, no nitric oxide synthase protein was detectable at any time in the galactosamine-treated cultures. Furthermore, addition of galactosamine after inducible nitric oxide synthase had already been synthesized (6.5 h after attachment) did not result in suppression of nitric oxide production in the hepatocyte cultures. The present studies suggest that galactosamine suppresses nitric oxide production in hepatocyte cultures by inhibiting synthesis of inducible nitric oxide synthase, rather than by interference in cellular uptake of arginine.     

纳米银胶/壳聚糖复合抗菌剂的制备及其在洗涤产品中抗菌性能

本文研究了纳米银胶/壳聚糖抗菌剂的制备及其形貌的表征分析,以大肠杆菌为代表菌株,研究了复合抗菌剂在洗涤产品中的抗菌效率及抗菌的稳定性,结果说明复合抗菌剂在洗涤产品中添加1.0%时,其抗菌效率达99%,经180 d长期分析,其抗菌活性仍保持95%左右。此外,复合抗菌剂对不同菌株的抗菌性能也均较强。     

Analysis and cryopreservation of hematopoietic stem and progenitor cells from umbilical cord blood

BACKGROUND: Umbilical cord blood (UCB) is an important source of hematopoietic stem and progenitor cells (HSC/HPC) for the reconstitution of the hematopoietic system after clinical transplantation. Cryopreservation of these cells is critical for UCB banking and transplantation as well as for research applications by providing readily available specimens. The objective of this study was to optimize cryopreservation conditions for CD34+ HSC/HPC from UCB. METHODS: Cryopreservation of CD34+ HSC/HPC from UCB after mononuclear cell (MNC) preparation was tested in a research-scale setup. Experimental variations were concentration of the cryoprotectant, the protein additive and cell concentration. In addition, protocols involving slow, serial addition and removal of DMSO were compared with standard protocols (fast addition and removal of DMSO) in order to avoid osmotic stress for the cryopreserved cells. Viability and recoveries of MNC, CD34+ cells and total colony-forming units (CFU) were calculated as read-outs. In addition, sterility testing of the collected UCB units before further processing was performed. RESULTS: The optimal conditions for cryopreservation of CD34+ HPC in MNC preparations were 10% DMSO and 2% human albumin at high cell concentrations (5 x 10(7) MNC/mL) with fast addition and removal of DMSO. After cryopreservation using a computer-controlled freezer, high viabilities (89%) and recoveries for CD34+ cells (89%) as well as for CFU (88%) were observed. Microbial contamination of the collected UCB samples was reduced to a rate of 6.4%. DISCUSSION: Optimized cryopreservation conditions were developed for UCB MNC in respect of the composition of the cryosolution. In addition, our results showed that fast addition of DMSO is essential for improved cryopreservation and post-thaw quality assessment results, whereas the speed of DMSO removal after thawing has little influence on the recoveries of CD34+ cells and CFU.     

Response of three phytoplankton bioassay techniques in experimental ponds of known limiting nutrient

In a controlled enrichment study of eight experimental ponds, results from the batch bioassay, primary productivity incubation bioassay, and chemostat techniques for measuring limiting factors of phytoplankton algae were compared to the change in the natural system with nutrient addition. In the ponds, rapid and dramatic increase in both phytoplankton biomass and primary productivity upon the addition of nitrogen and phosphorus fertilizer offered conclusive evidence that these nutrients were limiting in the control ponds to which no nutrients were added. Both the batch bioassay and chemostat techniques clearly indicated nitrogen and possibly phosphorus as the limiting factors; however, the primary productivity incubation bioassay technique showed no increase in ¹⁴C uptake with addition of these nutrients. A species- and/or nutrient-specific time lag between nutrient uptake and increased carbon fixation is suggested to explain the failure of the technique to yield positive results within the 4-hour incubation period used.     

Analysis of the effects of erythrocytes on mitogen-dependent clonal proliferation of murine B lymphocytes

Addition of intact erythrocytes to semisolid agar cultures of murine B cells dramatically improves cloning efficiency and affects colony morphology. In this study, we investigated possible mechanisms through which this might occur. Specific modification of sheep erythrocyte (SRBC) membranes by treatment with trypsin but not other enzymes improved colony potentiation and erythrocytes from rats, mice, and humans were also effective after trypsin treatment. In addition, autoantibody-coated murine erythrocytes were superior to normal cells in this regard. These observations suggest that erythrocytes enhance lymphocyte survival and/or proliferation by means of particular membrane-mediated processes. The possible importance of erythrocytes as scavengers of toxic hydroxyl radicals was also investigated. Deliberately generated radicals formed by addition of dihydroxyfumaric acid and iron were effectively countered by addition of SRBC. More detailed analyses revealed that of several endogenously produced toxic species, hydrogen peroxide may be the most important under ordinary culture conditions. That is, addition of catalase but not Superoxide dismutase or mannitol improved cloning efficiency in cultures lacking SRBC. These studies suggest that erythrocytes have a beneficial effect on lymphocyte survival and function in culture through at least two mechanisms.     

Interactive effects of water and nitrogen addition on soil microbial communities in a semiarid steppe

Aims Better understanding of microbial compositional and physiological acclimation mechanisms is critical for predicting terrestrial ecosystem responses to global change. The aim is to assess variations in soil microbial communities under future scenarios of changing precipitation and N deposition in a semiarid grassland of northern China.Methods In order to explicitly estimate microbial responses, a field experiment with water and N addition was established in April 2005 and continuously conducted for 4 years. Specifically, soil microbial community composition and microbial C utilization potential were determined by phospholipid fatty acid (PLFA) and community-level physiological profiles, respectively.Important findings Water addition had no effects on the PLFA concentrations of gram-positive (GP) and negative bacteria (GN), total bacteria and fungi. However, N addition caused significant reductions in the PLFA concentrations of GP, GN, total bacteria and fungi and thus decreased total PLFA of microbial communities. Moreover, there were interactive effects of water and N addition on GN/GP and the ratio of fungal to bacterial PLFA (F/B). In addition, synergistic effects were found between water and nitrogen in affecting microbial C utilization potentials, which implies that microbial C utilization potentials tend to be enhanced when both N and water availability are sufficient. Overall, the microbial responses to water and N addition support our hypothesis that water and N addition may be combined together to affect microbial communities in the semiarid grassland.     

半干旱黄土区不同管理措施下草地群落结构对短期氮、水添加的响应

氮沉降和降水变异显著影响草地群落结构和功能,但缺乏对不同管理措施下草地群落结构对氮沉降和降水变异响应的研究。为模拟不同管理措施下草地群落结构对氮沉降和降水变异的响应特征,以半干旱黄土区云雾山国家自然保护区典型草原为研究对象,系统分析了在封育、刈割和火烧三种管理措施下,氮添加和水添加对群落地上生物量、功能群组成和群落多样性的影响。结果表明,氮添加和水添加对地上生物量、功能群组成和群落多样性指数的影响因管理措施不同有所差异。（1）在封育草地上,氮添加显著降低物种多样性,对地上生物量影响较小;水添加显著增加物种多样性指数,氮添加和水添加的交互作用显著增加地上生物量、禾本科所占比例和莎草科所占比例;物种多样性指数均与地上生物量无显著相关,与不同功能群所占比例显著相关。（2）在刈割草地上,氮添加和水添加显著提高草地群落地上生物量,氮添加和水添加交互作用尤为显著;氮添加和水添加显著增加物种丰富度指数,对物种均匀度影响较小;杂草类所占比例和地上生物量对Shannon-Weiner多样性指数的贡献率较大。（3）在火烧草地上,氮添加和水添加显著提高群落地上生物量,对物种多样性的影响因年份不同有所差异,氮添加和水添加交互作用具有累加效应;Shannon-Weiner多样性指数与地上生物量呈显著负相关,与莎草科所占比例呈显著正相关。研究表明管理措施显著影响群落结构对氮添加和水添加的响应特征,亦改变生产力和物种多样性的关系模式,为更好地应对全球变化进行草地管理提供数据支撑。     

Effects of experimental water addition depend on grassland community characteristics

Plant community biomass and composition on low-productivity soils, such as serpentine, may be more resistant to climate change because they host stress-tolerant species that may respond slowly to change. These communities also host a number of endemic taxa that are of special interest because of their narrow distributions. In a 3-year study, we experimentally tested the response of serpentine and non-serpentine communities to water addition in spring. We also compared the responses of endemics and generalists to water addition, with and without biomass (competitor) removal. In the non-serpentine grassland, peak biomass was significantly greater in the water addition plots compared with control plots, but this effect depended on the year. In the serpentine grassland, there was no effect of water addition on biomass. Survival, biomass, growth rates, and seed production of soil endemics and generalists were all significantly reduced by competition, but were unaffected by water addition. Overall, endemics tended to perform better in serpentine soil and generalists in non-serpentine soil, suggesting that soil is an important factor for the establishment and survival of endemics and generalists. For endemics, the effect of biomass removal was stronger on non-serpentine soil, but for generalists this effect was similar on both soils, indicating that competition can be important in low-resource habitats. In conclusion, our results suggest that low-fertility plant communities may be slow to respond to changes in precipitation compared to communities on more fertile soil.     

氮沉降对毛竹林土壤可溶性有机质数量与光谱学特征的影响

中国亚热带是受氮沉降影响最严重的地区之一.土壤可溶性有机质(DOM)被认为是土壤有机质的重要指标,氮沉降可能通过改变微生物活性导致土壤DOM质量和数量的变化.本研究以亚热带毛竹林为研究对象,设置对照、低氮和高氮3个水平,进行为期3年的施氮处理,探究氮添加对土壤DOM含量、光谱学特征和微生物胞外酶活性的影响.结果表明: 与对照相比,施氮后土壤pH、可溶性有机碳、可溶性有机氮含量和芳香化指数无显著变化,而腐殖化指数随施氮量的增加显著增加,微生物酶活性也随着施氮量的增加呈现先升高后下降的趋势.傅里叶红外光谱结果显示,土壤DOM在7个区域的相似位置存在吸收峰,其中,1000～1260 cm^-1的吸收峰最强,表明施氮处理后,土壤中多糖类、醇类、羧酸类及酯类物质增加.三维荧光光谱结果表明,施氮处理后,土壤DOM结构有显著改变,表现在低分子物质如类蛋白质物质和微生物代谢产物减少,而高分子物质如类腐殖质物质显著增加.总的来说,施氮使得土壤氮与微生物需求相适应,促进微生物分解DOM中易降解的物质,土壤DOM结构更加复杂,短期氮沉降可能有利于土壤肥力的改善.     

小麦-黑麦附加系的创制及5R抗白粉病新基因的发现

以重复序列pAS1和pSc119.2为探针,对八倍体小黑麦×普通小麦的F5代植株进行了FISH分析,同时对这些材料进行了田间抗病性鉴定。从中鉴定出了1R、2R、3R、4R、5R、6R、7R单体附加系和1R、2R二体附加系,1R和4R附加系出现频率相对较高。5R和6R单体附加系对白粉病免疫,推测5R染色体上带有新的白粉病抗性基因。此外,还检测到不少植株染色体组发生了变异,且小麦4B染色体优先缺失。     

Variation of the Wheatgrass Chromosomes in Wheat-wheatgrass Disomic Addition Line TAI 14 Revealed by Fluorescence in Situ Hybridization

The karyotype of the primary wheat-wheatgrass disomic addition line TAI-14 was 2n = 44 in which all of the chromosomes were metacentric and submetacentric. However, in the progeny of the TAI-14, a pair of telocentric chromosomes were observed. In order to clarify whether the telocentric chromosomes were of common wheat or of wheatgrass, the fluorescence in situ hybridization (FISH) technique was employed. It was revealed that the wheat chromosomes exhibited red fluorescence while the ditelocentric chromosomes green fluorescence. Therefore, the primary TAI-14 was conversed from the disomic addition line into the ditelocentrie addition line. The possible explanation for such a variation and the potential significance of the ditelocentric addition line were discussed briefly.     

The responses of lake waters to organic matter additions

The increase of inorganic nitrogen subsequent to the addition of organic matter was investigated in replicate lake-water aliquots. Two experiments used freshly killed bacteria as the organic addition. In both, inorganic nitrogen in the water column increased only after a lag period following the organic addition, and only if the amount of organic matter added exceeded a threshold value. Two other experiments used freshly killed algae as the organic addition; in these, neither the lag period nor the threshold value were seen. A qualitative explanation for these observations is offered.