施肥进步在粮食增产中的贡献及其地理分异

采用中长期田间试验对８种模拟施肥模型在温带的海伦试验站、暖温带的沈阳试验站和亚热带的桃源试验站进行了６～１０年试验,以比较、评价施肥在粮食生产中的贡献．结果发现,施肥在作物产量形成中的贡献随施肥制度和气候的热量因素所影响;在最佳施肥条件下,施肥在产量中的贡献率分别为海伦（温带）３０％、沈阳（暖温带）３８％、桃源（亚热带）４４％．按这一实验结果可以一般地估计：当其他技术条件不变时,施肥在产量形成中的贡献率最高可达３０～４５％,随所在地区气候的热量条件而不同．     

Association between cytokines and methylation of SOCS-1 in serum of patients with ankylosing spondylitis

In this study, we aim to determine the relationship between methylation level of an inflammatory-related gene, SOCS-1 in serum samples of patients with ankylosing spondylitis (AS) and their degree of inflammation as well as serum cytokine level. Quantitative real time methylation specific PCR was performed to examine the promoter methylation of SOCS-1 in serum samples of 43 HLA-B27+ AS patients and 6 B27+ healthy controls. Degree of inflammation was accessed by spondylopathy, sacroiliitis as well as acute phase reactant, erythrocyte sedimentation rate and C-reactive protein (CRP). Serum IL-6 and TNF-α level was determined by ELISA assay. SOCS-1 methylation can only be found in serums samples from patients but not normal control. Methylation of SOCS-1 significantly associated with severity of patient’s spondylopathy (P < 0.005), sacroiliitis (P < 0.005) and acute phase reactant CRP (P = 0.0278). AS patients also exhibited higher serum IL-6 (P < 0.001) and TNF-α level (P < 0.001). Importantly, patients with high serum IL-6 or TNF-α level demonstrated a significantly higher SOCS-1 methylation (P < 0.001). In conclusion, this proof-of-principle study suggested that methylation of SOCS-1 can be detected in serum of HLA-B27+ AS patients but not in B27+ controls. The pathogenic potential of SOCS-1 methylation in AS deserves further investigation.     

Enhanced enzymatic hydrolysis of wheat straw by aqueous glycerol pretreatment

Considering the practical technology-economy of glycerol processing from oleochemicals industry, the ensuing work was proposed to further explore the atmospheric aqueous glycerol autocatalytic organosolv pretreatment (AAGAOP) to improve the enzymatic hydrolysis of lignocellulosic biomass. With the liquid-solid ratio of 20 g g(-1) at 220 degrees C for 3h, the AAGAOP enabled wheat straw to remove approximately 70% hemicelluloses and approximately 65% lignin, with approximately 98% cellulose retention. The pretreated fiber was achieved with approximately 90% of the enzymatic hydrolysis yield after 48 h. At oven-drying, dehydration was likely to cause the hornification of fiber, which was responsible for the low enzymatic hydrolysis of dried fiber. With SEM observations, the AAGAOP disrupted wheat straw into thin and fine fibrils, with a small average size and more surface area. The AAGAOP technique, as a novel strategy, enhanced the enzymatic hydrolysis of lignocellulosic biomass by removing the chemically compositional barrier and altering the physically structural impediment.     

Balb/C乳鼠小脑Purkinje细胞原代培养方法

目的建立一种简单、有效的Balb/C乳鼠小脑Purkinje细胞原代培养方法,并初步研究其细胞电生理特性。方法钝性分离生后24h内的乳鼠小脑,采用低浓度胰蛋白酶加机械吹打法获得单细胞悬液,然后用含10%胎牛血清的DMEM/F12培养,24h候更换为1%N2+1%T3+1%谷氨酰胺的DMEM/F12维持培养,3-5d天后进行细胞免疫荧光染色,7-9d天后用全细胞膜片钳单通道法记录钙电流。结果该方法培养的神经元形态典型,细胞学鉴定阳性率高(70%),并能记录到钙通道电流。结论该方法取材容易,操作简便,且培养出的原代Purkinje细胞生长状态较好,神经元的活性较高,可用于电生理研究。     

抑制O~6-甲基鸟嘌呤-DNA甲基转移酶活性与肿瘤细胞对亚硝脲药物敏感性关系的研究

80％以上的肿瘤细胞为O~6-甲基鸟嘌吟-DNA甲基转移酶(O~6-MT)活性较高的Mer~+型,能够修复亚硝脲药物(NU)造成的DNA烷化损伤,对NU不敏感。本实验证明,用0.75,0.50和0.25mmol/L甲基亚硝脲(MNU)分别处理Mer~+型的HeLaS3,SMMC-7721和表现Mer~-型特征的Cc801,均能明显降低细胞中O~6-MT活性,从而显著提高了三种细胞对嘧啶亚硝脲和双氯乙亚硝脲的敏感性,提示降低O~6-MT活性是使用NU对Mer~+型肿瘤进行有效治疗的前提。     

Infection of human dendritic cells by a sindbis virus replicon vector is determined by a single amino acid substitution in the E2 glycoprotein

The ability to target antigen-presenting cells with vectors encoding desired antigens holds the promise of potent prophylactic and therapeutic vaccines for infectious diseases and cancer. Toward this goal, we derived variants of the prototype alphavirus, Sindbis virus (SIN), with differential abilities to infect human dendritic cells. Cloning and sequencing of the SIN variant genomes revealed that the genetic determinant for human dendritic cell (DC) tropism mapped to a single amino acid substitution at residue 160 of the envelope glycoprotein E2. Packaging of SIN replicon vectors with the E2 glycoprotein from a DC-tropic variant conferred a similar ability to efficiently infect immature human DC, whereupon those DC were observed to undergo rapid activation and maturation. The SIN replicon particles infected skin-resident mouse DC in vivo, which subsequently migrated to the draining lymph nodes and upregulated cell surface expression of major histocompatibility complex and costimulatory molecules. Furthermore, SIN replicon particles encoding human immunodeficiency virus type 1 p55(Gag) elicited robust Gag-specific T-cell responses in vitro and in vivo, demonstrating that infected DC maintained their ability to process and present replicon-encoded antigen. Interestingly, human and mouse DC were differentially infected by selected SIN variants, suggesting differences in receptor expression between human and murine DC. Taken together, these data illustrate the tremendous potential of using a directed approach in generating alphavirus vaccine vectors that target and activate antigen-presenting cells, resulting in robust antigen-specific immune responses.     

糖皮质激素抑制加压素释放的细胞膜机制

利用离休孵育脑薄片和放射免疫测定其释放的精氨酸加压素（ＡＶＰ）方法,探讨糖皮质激素（ＧＣ）在不能进入细胞内的情况下,对去肾上腺大鼠的下丘脑薄片释放ＡＶＰ的快速影响及其可能的细胞膜机制。结果如下：（１）下丘脑薄片能够稳定地释放ＡＶＰ（２ｈ）,其释放量为１５．４２±１．２８ｐｇ／ｍｉｎ;（２）牛血清白蛋白耦联皮质酮（Ｂ－ＢＳＡ）对ＡＶＰ的释放具有快速的（２０ｍｉｎ）抑制性效应,在１０￣（－７）─１０￣（－４）ｍｏｌ／Ｌ范围内呈剂量一效应关系;（３）ＧＣ细胞内受体拮抗剂ＲＵ４８６（１０￣（－４）─１０￣（－３）ｍｏｌ／Ｌ）能部分地阻断Ｂ─ＢＳＡ的快速抑制效应;（４）孵育液中Ｃａ￣（２＋）程度升高,Ｂ─ＢＳＡ的快速抑制效应明显增强;反之,孵育液中无Ｃａ￣（２＋）则Ｂ－ＢＳＡ的快速抑制效应有所减弱。表明ＧＣ在未进入细胞内的情况下也可快速地抑制大鼠下丘脑薄片释放ＡＶＰ,因此没有通过传统的基因组机制,而是由非基因组机制介导的,其作用部位在细胞膜水平上,可能是影响Ｃａ￣（２＋）的跨细胞膜内流通量或／和影响有Ｃａ￣（２＋）参与的ＡＶＰ释放过程的结果。     

多级逆流工艺促进城市污泥厌氧发酵生产挥发性脂肪酸

采用一种新型的厌氧发酵工艺——多级逆流发酵工艺对城市污泥进行厌氧发酵, 实现高效产挥发性脂肪酸的目的。结果表明, 实验条件下应用多级逆流发酵工艺, 挥发性脂肪酸浓度与产率分别达到(10.5±0.5) g/L和0.20 gVFAs/ gVS, 与普通厌氧发酵工艺相比, 分别提高了31%和54%。此外, 在多级逆流工艺中, 底物有机质去除率可达50%, 较普通厌氧发酵提高了37%。进一步分析多级逆流工艺产酸的机制, 发现产酸效率的提高在于降低了发酵产物对厌氧产酸细菌的抑制效应, 并且工艺的VFAs产率以及有机质去除率分别取决于第一级和第三级厌氧发酵过程。因此, 城市污泥采用多级逆流工艺厌氧发酵不仅能够有效促进挥发性脂肪酸的生成, 而且能够较大程度上提高污泥中有机质的去除率。     

ATM phosphorylates histone H2AX in response to DNA double-strand breaks

A very early step in the response of mammalian cells to DNA double-strand breaks is the phosphorylation of histone H2AX at serine 139 at the sites of DNA damage. Although the phosphatidylinositol 3-kinases, DNA-PK (DNA-dependent protein kinase), ATM (ataxia telangiectasia mutated), and ATR (ATM and Rad3-related), have all been implicated in H2AX phosphorylation, the specific kinase involved has not yet been identified. To definitively identify the specific kinase(s) that phosphorylates H2AX in vivo, we have utilized DNA-PKcs-/- and Atm-/- cell lines and mouse embryonic fibroblasts. We find that H2AX phosphorylation and nuclear focus formation are normal in DNA-PKcs-/- cells and severely compromised in Atm-/- cells. We also find that ATM can phosphorylate H2AX in vitro and that ectopic expression of ATM in Atm-/- fibroblasts restores H2AX phosphorylation in vivo. The minimal H2AX phosphorylation in Atm-/- fibroblasts can be abolished by low concentrations of wortmannin suggesting that DNA-PK, rather than ATR, is responsible for low levels of H2AX phosphorylation in the absence of ATM. Our results clearly establish ATM as the major kinase involved in the phosphorylation of H2AX and suggest that ATM is one of the earliest kinases to be activated in the cellular response to double-strand breaks.