科尔沁沙地樟子松人工林不同年龄针叶生理生态性状

樟子松(Pinus sylvestris var. mongolica)又称蒙古松, 是我国“三北”防护林建设的主要造林树种。人工林建立初期, 在水分、养分匮乏的干旱、半干旱沙地, 樟子松仍表现出较强的适应性; 近年来, 各地樟子松人工林均出现衰退迹象。在沙地这种特殊生境下, 樟子松针叶的光合作用、水分利用效率、氮利用效率等主要性状的研究对于理解樟子松的沙地适应性具有非常重要的意义。该文以位于科尔沁沙地南缘的中国科学院寒区旱区环境与工程研究所奈曼沙漠化研究站(42°55′ N, 120°43′ E) 30龄樟子松人工林为研究对象, 对不同年龄针叶的光合作用、蒸腾作用、针叶碳氮含量、针叶形态(叶长、宽、厚)等主要生理生态属性进行测定, 计算出针叶的蒸腾系数(K_c)、光合氮利用效率(PNUE), 阐明了这些性状与樟子松叶龄的关系, 进而探讨了叶片性状在樟子松适应沙地生境中的意义。结果表明, 1)不同年龄针叶的光合速率(P_n)、K_c和PNUE存在显著差异, 四龄针叶的P_n、K_c和PNUE显著低于其他龄针叶。氮含量减少是导致P_n差异的根本原因, P_n随着氮含量的减小而降低。2)各龄针叶的长、宽等形态参数及碳含量受其形成前一年的降水量影响显著。3)从水分及养分利用(K_c、PNUE)角度来看, 一至三年生针叶的利用效率更高, 四龄针叶较低。合理的叶龄结构既能增强针叶对氮素的利用又能增大植株的光合叶面积, 有利于提高个体乃至冠层的光合能力。此外, 遇到严重干旱时, 老叶脱落可以增强樟子松个体的适应性。     

两种立地条件下麻栎人工林地上部分养分的积累和分配

麻栎(Quercus acutissima)是一种分布广、用途大、耐干旱瘠薄的乔木树种, 掌握其生长规律和养分利用特性对麻栎人工林的科学经营十分必要。对安徽省滁州市红琊山林场两种立地条件下的麻栎人工林的生长和养分状况进行了对比研究, 结果表明: 在土壤含石量较高、养分含量较少的立地条件下, 12年生的麻栎人工林地上部分生物量为49 180.2 kg·hm^-2; 林木养分总累积量为633.9 kg·hm^-2, 其中N、P、K、Ca、Mg的累积量分别为119.9、18.7、88.5、368.6和38.2 kg·hm^-2。在土壤含石量较少、养分含量较高的立地条件下, 12年生麻栎人工林地上部分生物量为90 774.8 kg·hm^-2; 林木养分总累积量为993.6 kg·hm^-2, 其中N、P、K、Ca、Mg的累积量分别为203.5、23.0、146.9、553.6和66.6 kg·hm^-2。所以, 立地条件对麻栎生长和养分累积具有显著影响。较差立地条件下的麻栎对土壤养分的富集系数较大, 但其凋落物的养分含量较低。研究显示, 麻栎可以通过养分奢侈吸收、提高养分内循环、减少养分损失等途径来适应低养分环境。     

铜胁迫对国槐幼苗生长及叶片生理特性的影响

采用盆栽方法研究了不同浓度处理水平的铜对国槐(Sophora japonica)生长及叶片部分生理指标的影响.结果表明:国槐幼苗的株高及地径随铜胁迫浓度的增加表现出先增加后下降的趋势,在浓度1000 mg·kg^-1时,株高和地径与对照相比达到极显著差异(检验水平,P<0.01).在浓度<500 mg·kg^-1时,叶绿素含量的呈下降趋势,细胞膜透性呈增加趋势,与对照相比差异不显著;脯氨酸含量与超氧化物歧化酶(SOD)活性迅速上升,与对照处理相比差异显著,表现出一定的适应能力.随着铜胁迫浓度的增加(>500 mg·kg^-1),叶绿素含量及SOD活性显著下降,MDA含量、相对电导率、脯氨酸含量显著上升,表明国槐幼苗受害明显加重.     

小鼠淋巴细胞抗原CTLA-4的胞外肽段表达及纯化

目的: 真核细胞表达小鼠淋巴细胞抗原CTLA-4胞外段肽,研究表达肽段与抗原呈递细胞B7分子结合后减轻小鼠淋巴细胞刺激后的增殖抑制,从而启动T淋巴细胞进一步增殖。方法:从小鼠脾脏淋巴细胞获得总RNA,通过逆转录PCR扩增出CTLA-4全长基因,克隆并测序。依据胞外段序列和真核表达载体pcDNA3.1序列,合成引物扩增胞外片段,两者经内切核酸酶处理、连接构建重组表达pcDNA3.1载体,重组质粒经测序验证后,采用lipofectamine 2000转染入小鼠肝癌细胞Hepa1-6,经G418筛选获得稳定表达细胞株。结果:获得小鼠CTLA-4胞外段真核表达载体和小鼠肝癌细胞Hepa1-6稳定表达转染细胞株,制备了CTLA-4胞外肽段,经His标签抗体和小鼠CTLA-4抗体Western blot检测表达蛋白带均呈阳性。结论:获得CTLA-4胞外段肽,为进一步研究该肽的作用打下基础。     

可改良棉粕蛋白的菌株选育及其发酵

棉粕蛋白质含量高达38％~50％,然而作为饲料其蛋白质品质较差,饲料利用率较低。为提高其蛋白质利用率,从自然界筛选出了能够高效降解棉粕大分子蛋白质的优良菌株4株,经生化与分子生物学试验鉴定为Bacillus subtilis(2株,编号为H1和H7),Bacillus cereus (1株,编号为H9)和Aspergillus niger (1株,编号为P1)。通过单菌及组合发酵实验比较发现:最适宜菌种组合为B. subtilis(H1)和A. niger (P1)。两菌株组合发酵后,棉粕TCA-NSI(三氯乙酸氮溶指数)提高了25.34%,小分子多肽含量提高了11%,游离必需氨基酸提高了24%,蛋白质的体外消化率由44.56%提高到了78.61%,明显高于其他菌种组合,研究结果表明其组合发酵可有效改良棉粕蛋白品质,显著提高棉粕蛋白的饲用价值。     

Molecular and cellular bases of chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative disease characterized by the overproduction of granulocytes, which leads to high white blood cell counts and splenomegaly in patients. Based on clinical symptoms and laboratory findings, CML is classified into three clinical phases, often starting with a chronic phase, progressing to an accelerated phase and ultimately ending in a terminal phase called blast crisis. Blast crisis phase of CML is clinically similar to an acute leukemia; in particular, B-cell acute lymphoblastic leukemia (B-ALL) is a severe form of acute leukemia in blast crisis, and there is no effective therapy for it yet. CML is induced by the BCR-ABL oncogene, whose gene product is a BCR-ABL tyrosine kinase. Currently, inhibition of BCR-ABL kinase activity by its kinase inhibitor such as imatinib mesylate (Gleevec) is a major therapeutic strategy for CML. However, the inability of BCR-ABL kinase inhibitors to completely kill leukemia stem cells (LSCs) indicates that these kinase inhibitors are unlikely to cure CML. In addition, drug resistance due to the development of BCR-ABL mutations occurs before and during treatment of CML with kinase inhibitors. A critical issue to resolve this problem is to fully understand the biology of LSCs, and to identify key genes that play significant roles in survival and self-renewal of LSCs. In this review, we will focus on LSCs in CML by summarizing and discussing available experimental results, including the original studies from our own laboratory.     

NLRP6在感染性和非感染性疾病中的作用

核苷酸结合寡聚化结构域样受体含pyrin结构域蛋白6(NLRP6)属于核苷酸结合寡聚化结构域样受体(NLRs)家族蛋白.NLRP6可以作为受体蛋白参与炎症小体的组装,引起白细胞介素IL-1β和IL-18的成熟与分泌.NLRP6在病原体感染诱导宿主天然免疫应答中发挥重要作用.此外,NLRP6在维持肠道上皮完整、调控代谢性...     

Soil N forms and gross transformation rates in Chinese subtropical forests dominated by different tree species

Background and aims

Knowledge related to extent of differing soil N forms and N transformation rates in subtropical southern China is severely limited. Accordingly, the purpose of this study was to investigate if and how tree species of different foliage types (coniferous, deciduous, and evergreen broadleaved) influence N forms and microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) content as well as gross N transformation rates in the organic and mineral soils of three distinct subtropical forests in China.

Methods

Chloroform fumigation extraction was used to determine MBC and MBN content while ¹⁵N-isotope dilution techniques were used to measure gross N transformation rates. Canonical correspondence analysis (CCA) was used to quantify relationships between soil chemical characteristics and changes in soil N transformation rates.

Results

Soil N forms, MBC and MBN content, and N transformation rates were found to be significantly different between tree species. Deciduous forest soil exhibited the highest N transformation rates. Soil N transformation rates were closely associated with total soil C and N and MBC and MBN content.

Conclusions

Soil substrate quantity and soil microbial activity play a more important role in soil N transformation processes than does soil quality in China’s subtropical forests. Tree species type should therefore be taken into account when trying to determine ecosystem N cycling.     

MicroRNA 421 suppresses DPC4/Smad4 in pancreatic cancer

Dihydroavenanthramide D (DHAvD) is a synthetic analog to naturally occurring avenanthramide, which is the active component of oat. Previous study demonstrates that DHAvD strongly inhibits activation of nuclear factor-kappa B (NF-κB), which is a major component in cancer cell invasion. The present study investigated whether DHAvD can modulate MMP-9 expression and cell invasion in MCF-7 human breast cancer cells. MMP-9 expression and cell invasion in response to 12-O-tetradecanoylphorbol-13-acetate (TPA) was increased, whereas these inductions were muted by DHAvD. DHAvD also suppressed activation of mitogen-activated protein kinase (MAPK), and MAPK-mediated nuclear factor-kappa B (NF-κB) and activator protein-1 (AP-1) activations in TPA-treated MCF-7 cells. The results indicate that DHAvD-mediated inhibition of TPA-induced MMP-9 expression and cell invasion involves the suppression of the MAPK/NF-κB and MAPK/AP-1 pathways in MCF-7 cells. DHAvD may have potential value in breast cancer metastasis.     

MicroRNA 421 suppresses DPC4/Smad4 in pancreatic cancer

MicroRNAs (miRNAs) have emerged as important regulators in the development of pancreatic cancer and may be a valuable therapeutic application. DPC4/Smad4 is a critical tumor suppressor involved in the progression of pancreatic cancer, but few studies have been conducted to determine its relationship with miRNAs. In this study, we identify miR-421 as a potential regulator of DPC4/Smad4. We find that in human clinical specimens of pancreatic cancer miR-421 is aberrantly upregulated while DPC4/Smad4 is strongly repressed, and their levels of expression are inversely correlated. Moreover, ectopic expression of miR-421 significantly decreases DPC4/Smad4 protein level in pancreatic cancer cell lines and simultaneously promotes cell proliferation and colony formation in vitro. Our findings identify miR-421 as a potent regulator of DPC4/Smad4, which may provide a novel therapeutic strategy for treatment of DPC4/Smad4-driven pancreatic cancer.