Involvement of abscisic acid and ethylene in the responses of rice grains to water stress during filling

This study was to test the hypothesis that the interaction between abscisic acid (ABA) and ethylene may be involved in mediating the effects of water stress on grain filling. Two high lodging‐resistant rice (Oryza sativa L.) cultivars were pot‐grown. Three treatments, well‐watered, moderate water‐stressed (MD), and severe water‐stressed (SD), were imposed from 9 d post‐anthesis until maturity. Grain filling rate and grain weight were significantly increased under MD but decreased under SD. The two cultivars behaved the same. ABA concentration in the grains was very low during the grain filling stage, reaching a maximum when the grain filling rate was highest. Both the grain filling rate and ABA concentration were substantially enhanced by water stress. In contrast to ABA, concentrations of ethylene and 1‐aminocylopropane ‐1‐carboxylic acid (ACC) in the grains were very high at early grain filling stage and sharply decreased during the linear period of grain growth. MD reduced, whereas SD remarkably increased, their accumulation. The ratio of ABA to ACC was increased in MD grains but decreased in SD grains, indicating that there was a greater enhancement of ABA concentration than ethylene production in the MD treatment only. Application of cobalt ion (inhibitor of ethylene synthesis) or ABA at the early grain filling stage significantly increased grain filling rate. Spraying with ethephon (ethylene‐releasing agent) or fluridone (inhibitor of ABA synthesis) had the opposite effect. The results suggest that antagonistic interactions between ABA and ethylene mediate the grain filling rate, and a high ratio of ABA to ethylene enhances grain filling rate.     

拉米夫定联合胸腺肽A1 治疗慢性乙型肝炎的疗效观察

目的:探讨拉米夫定(LAM)联合胸腺肽α1(Tα1)治疗慢性乙型肝炎的长期疗效和安全性。方法:72例慢性乙肝患者(HBV-DNA和HBeAg均阳性),按1:1随机分配进入联合治疗组(LAM+Tα1组)和单用拉米夫定组(LAM组)。结果:治疗1年时LAM+Tα1组HBeAg血清转换率(44.4%,16/36例)明显高于LAM组(5.6%,2/36例),P<0.01。停药1年后,持续的HBeAg血清转换率分别为36.1%(13/36例)和8.3%(3/36例),P<0.01。治疗过程中及停药后,两组HBV-DNA水平均明显下降,但两组的HBV-DNA转阴率相仿。治疗后1年ALT复常率联合治疗组与拉米夫定组相似,分别为75%(27/36例)和66.7%(24/36例)、随访1年时ALT复常率联合治疗组明显高于拉米夫定组,分别为58.3%(21/36例)和16.7%(6/36例)。在治疗过程中,未发现严重的不良反应。结论:LAM联合Tα1治疗慢性乙肝,不良反应少,疗效优于单一LAM用药组。     

过表达PINK1抵抗鱼藤酮引起多巴胺神经元损伤的研究

目的:明确在C57BL/6小鼠纹状体过表达野生型的人源帕金森相关蛋白PINK1能否减轻由侧脑室注射鱼藤酮引起多巴胺神经元损伤。方法:通过向C57BL/6小鼠(雄性,7周龄,18~20g)左侧纹状体中注射带有GFP人源野生型PINK1及突变体PINK1^G309D的慢病毒包装颗粒,两周后向小鼠左侧侧脑室中定位注射鱼藤酮,通过蛋白质印迹,免疫组化和行为学的方法检测PINK1对鱼藤酮引起多巴胺神经元损伤的影响。结果:蛋白质印迹和免疫组化的实验都证明了在C57BL/6小鼠纹状体过表达野生型的PINK1对于鱼藤酮引起多巴胺能神经元的减少有明显的抑制作用(P<0.01),但对鱼藤酮引起的行为学损伤没有明显的改善作用。     

Biosynthesis of yeast mannan : Diversity of mannosyltransferases in the mannan-synthesizing enzyme system from yeast

1. A microsomal enzyme preparation from the yeast Saccharomyces cerevisiae catalyzes the transfer of mannosyl units from GDPmannose to mannose and a number of mannose-containing oligosaccharides and glycosides whereby different glycosidic bonds are formed.2. Of the compounds tested besides mannose, only those containing an α-linked mannosyl unit at the nonreducing position of their moleculae were effective as receptors. Monodeoxyanalogues of mannose as well as α-mannose phosphates did not serve as receptors in the above reaction.3. The structure of the product formed with mannose as receptor was determined to be O-α-D-mannosyl-(1→2)-mannose; with αMan(1→Man(1→6)mannose as the acceptor, the product was αMan(1→6)αMan(1→6)mannose and with αMan-(1→2)mannose the product was tentatively characterized as a mixture of αMan-(1→3)αMan(1→2)mannose and αMan(1→2)αMan(1→2)mannose.4. The enzymes catalyzing the formation of different types of glycosidic bonds differed in their acceptor specificity, pH-activity curves and rates of heat denaturation.5. Radioactive disaccharids were unable to enter the mannan protein molecule in the cell-free system while free radioactive mannose did incorporate into polysacchride to a minor extent under the same conditions.     

Endothelin-1 enhances cell migration through COX-2 up-regulation in human chondrosarcoma

Background

Chondrosarcoma is a type of highly malignant tumor with a potent capacity of local invasion and distant metastasis. The effect of endothelin-1 (ET-1) on migration activity in human chondrosarcoma cells is not clearly understood. Here, we found that ET-1 increased the migration and expression of cyclooxygenase (COX)-2 in human chondrosarcoma cells.

Methods

ET-1-mediated COX-2 expression was assessed by qPCR and Western blot analysis. The mechanisms of action of ET-1 in different signaling pathways were studied using Western blotting. Knockdown of proteins was achieved by transfection with siRNA. Chromatin immunoprecipitation assays were used to study in vivo binding of c-Jun to the COX-2 promoter.

Results

Human chondrosarcoma tissues had significant expression levels of ET-1 and COX-2, which were higher than that in normal cartilage. Exogenous ET-1 increased cell migration and the expression of COX-2. In addition, COX-2 protein levels and cell migration ability were abolished by ET receptor antagonists. Activation of the mitogen-activated protein kinase (MAPK) and activator protein-1 (AP-1) pathways after ET-1 treatment was demonstrated, and ET-1-induced COX-2 expression and cell migration activity were inhibited by the specific inhibitor and mutant of MAPK and AP-1 cascades. ET-1 increased the binding of c-Jun to the AP-1 element on the COX-2 promoter. Furthermore, knockdown of ET-1 decreased cell metastasis in vitro and in vivo.

Conclusions

Our results indicated that ET-1 enhances the cell migration of chondrosarcoma by increasing COX-2 expression through the ET receptors, MAPK, and AP-1 signal transduction pathway.

General significance

We link high ET-1 and COX-2 expression to chondrosarcoma.     

膜蛋白Presenilin 1的跨膜结构及催化机制

膜蛋白presenilin 1(PS1)是γ分泌酶的催化组分,是催化产生β淀粉样蛋白（β-amyloid,Aβ）的关键蛋白酶,因此也是治疗阿尔茨海默病（Alzheimer’s disease,AD）的主要靶点.PS1属于膜内裂解蛋白酶家族,这是一类在膜脂双层内部催化肽键水解断裂的蛋白酶.PS1其独特的跨膜结构和催化机制虽然还未完全揭示,但近期相关的研究取得了重要成果：PS1有10个疏水区,跨膜9次,其N端位于胞内,C端位于胞膜外或者内质网腔内,亦或不同程度地插入膜内,2个起催化作用的天冬氨酸残基都位于疏水性的膜内,膜蛋白底物被催化水解时必须先结合到酶的疏水表面上来,然后再进入位于活性部位.虽然PS1的晶体从未获得,但2006年首次解析的膜内裂解蛋白酶GlpG的晶体结构和所提出的催化机理为PS1催化机理的揭示奠定了基础,也为设计和筛选PS1/γ分泌酶的特异性抑制剂提供了理论依据.     

Blood group H active glycolipid from rat ascites hepatoma AH 7974F.

A new type of fucose-containing glycolipid exhibiting blood group H activity was isolated from rat ascites hepatoma cell AH 7974F. As a result of studying its structure by partial acid hydrolysis, enzymatic degradation and immuno-precipitation reaction, the structure was tentatively proposed as Fuc(1 → 2)Gal(1 → 3)GalNAc(1 → 4)Gal(1 → 4)Glc(1 → 1)Cer.     

Moderate hypothermia suppressed excessive generation of superoxide anion radical and inflammatory reactions in blood and liver in heatstroke: Laboratory study in rats

Abstract

The study was performed to demonstrate superoxide radical (O₂·–) generation, systemic inflammation and liver injury caused by heatstroke and to reveal suppressive effects of moderate hypothermia. Heatstroke was defined as achieving pharyngeal temperature of 40°C with arterial pressure reduction. Heatstroke rats were divided to four groups by the temperature after the onset; 40°C, 37°C, 32°C and sham-treated with 37°C. O₂·– current was measured continuously in the right atrium using an electrochemical O₂·– senor. The O₂·– current increased in all groups except for the sham-treated group during the induction. After the onset of heatstroke, the O₂·– current was suppressed with temperature-dependency. Plasma and liver high-mobility group box 1, intercellular adhesion molecule-1, plasma aspartate aminotransferase and alanine aminotransferase were also suppressed with the suppression of O₂·– generation. Therefore, excessive O₂·– generation might be a key factor in heatstroke and the suppression with moderate hypothermia would be a therapeutic modality.     

Induction of DNA single-strand breaks in barley by sodium azide applied at pH 3.

Sodium azide (1 to 50 mM), adjusted to pH 3 and applied for 2 h to presoaked barley seeds, induced a dose-dependent frequency of single-strand breaks in DNA of non-germinating embryos. This was demonstrated by sedimentation analyses of isolated DNA samples in alkaline sucrose gradients and in neutral sucrose gradients with 80% formamide. The doses applied also inhibited dose dependently the root length, seed germination and partially the seedling height. Only the sub-lethal doses (10 and 12.5 mM) induced a low frequency of chromatid breaks and translocations in the root tip metaphases. The sedimentation rate (in alkaline sucrose gradients) of calf thymus DNA treated with sodium azide at pH 3, was similar to that of the control DNA treated with buffer (pH 3) alone.     

Dexamethasone induces an increase in intracellular and membrane-associated lipocortin-1 (annexin-1) in rat astrocyte primary cultures

Summary 1. The antiinflammatory actions of glucocorticoid steroids are thought to occur through induction of the protein lipocortin-1 (LC-1; annexin-1). The purpose of the current study was to investigate whether astrocytic LC-1 content was increased in the presence of a synthetic glucocorticoid, dexamethasone.2. Steroid-induced changes in cellular levels of LC-1 in astrocytes were determined by electrotransfer and immunoblotting techniques. Separate cell fractions were investigated to study the influence of dexamethasone on astroglial LC-1 content. The effect of culture state on LC-1 expression was also examined.3. Intracellular LC-1 content was found to decrease after initiation of culture, with a substantial rise in both cell proliferation and LC-1 expression occurring after the replenishment of medium containing steroid-free serum. A further increase in intracellular LC-1 occurred upon incubation with dexamethasone. The glucocorticoid-induced change in intracellular LC-1 was a time-dependent event and coincided with an increase in membrane-associated LC-1.4. The findings in this study indicate that astrocytic LC-1 content is influenced by cell culture conditions and, in the presence of glucocorticoid steroids, the cellular localization of LC-1 is altered. This may indicate that LC-1 has functions at more than one cellular locality.     

Alpha-helix 1 in the DNA-binding domain of heat shock factor 1 regulates its heat-induced trimerization and DNA-binding

Heat shock factor 1 (HSF1) primarily regulates various cellular stress responses. The role of α-helix1 (H1) in its DNA-binding domain (DBD) during HSF1 activation remains unknown. Here, HSF1 lacking H1 loses its heat-induced activity, suggesting the importance of the latter. Furthermore, the CD spectra and AMBER prediction show that this H1 deficiency does not change the structure of HSF1 monomer, but does impact its heat-induced trimerization. Point mutation showed that Phe18 in H1 interacts with Tyr60, and that Trp23 interacts with Phe104 by an aromatic-aromatic interaction. Thus, the presence of H1 stabilizes the DBD structure, which facilitates the heat-induced trimerization and DNA-binding of HSF1.     

低氧对高原鼠兔和大鼠血液NO 与ET-1的影响

将Wistar大鼠暴露于3 780 m低氧环境,分别于24 h、2 wk及3 wk后采用酶联免疫法和硝酸还原酶法测定血液中的ET~(-1)和NO的含量,计算NO/ET~(-1)值,并与高原鼠兔比较,探讨低氧条件下大鼠与高原鼠兔血液中NO与ET~(-1)含量的变化趋势。结果表明,低氧24 h后,大鼠血液中NO和ET~(-1)的含量显著高于同海拔的高原鼠兔(P<0·01),而NO/ET~(-1)值无显著差异(P>0·05)。随着大鼠在高海拔停留时间的延长,血液中NO含量呈减少趋势,而ET~(-1)则有上升趋势,二者呈显著的负相关(r2=0·2416,P<0·01)。高原鼠兔NO/ET~(-1)值约为大鼠低氧2 wk和3 wk的2倍(P<0·01)。说明不同低氧暴露时间,高原鼠兔和大鼠的NO、ET~(-1)及NO/ET~(-1)值有显著差异,提示NO/ET~(-1)值可以作为有机体是否适应高原低氧环境的一个指标。     

运用染色质免疫沉淀技术筛选出AP-2α的靶基因GALK1

在后基因组时代,DNA-蛋白质的相互作用是研究基因表达调控的一个重要领域.与其他方法相比,染色质免疫沉淀技术 (chromatin immunoprecipitation assay, ChIP ) 是一种近来研究体内 DNA 与蛋白质相互作用的最好方法之一.本研究利用 ChIP 克隆方法, 找出了 AP-2α所调控的新的下游靶基因 GALK1,并应用 Luciferase assay和 RT-PCR 实验进行了初步的验证.这一新发现,有利于我们进一步研究转录因子AP-2α的功能.     

Endo-beta-galactosidase of Escherichia freundii. Hydrolysis of pig colonic mucin and milk oligosaccharides by endoglycosidic action.

The purified keratansulfate degrading enzyme from $\text{Eschericia freundii}$ could hydrolyze desialyzed pig colonic mucin and milk oligosaccharides. Desialyzed pig colonic mucin was digested to produce GlcNAcβ(1→3)Gal, GlcNAc-6Sβ(1→3)Gal and resistant polymer. Lacto-N-tetraose and lacto-N-tetraitol were hydrolyzed endoglycosidically to release glucose and sorbitol, respectively. Therefore, this enzyme was found to be an endo-β-galactosidase of rather wide specificity.     

Intra and extravascular transmembrane signalling of angiopoietin-1-Tie2 receptor in health and disease

Angiopoietin-1 (Ang-1) is the primary agonist for Tie2 tyrosine kinase receptor (Tie2), and the effect of Ang-1-Tie2 signalling is context-dependent. Deficiency in either Ang-1 or Tie2 protein leads to severe microvascular defects and subsequent embryonic lethality in murine model. Tie2 receptors are expressed in several cell types, including endothelial cells, smooth muscle cells, fibroblasts, epithelial cells, monocytes, neutrophils, eosinophils and glial cells. Ang-1-Tie2 signalling induces a chemotactic effect in smooth muscle cells, neutrophils and eosinophils, and induces differentiation of mesenchymal cells to smooth muscle cells. Additionally, this signalling pathway induces the secretion of serotonin, matrix metalloproteinases (MMPs) and plasmin. Ang-1 inhibits the secretion of tissue inhibitor of matrix metalloproteinase (TIMPs). Aberrant expression and activity of Tie2 in vascular and non-vascular cells may result in the development of rheumatoid arthritis, cancer, hypertension and psoriasis. Ang-1 has an anti-inflammatory effect, when co-localized with vascular endothelial growth factor (VEGF) in the vasculature. Thus, Ang-1 could be potentially important in the therapy of various pathological conditions such as pulmonary hypertension, arteriosclerosis and diabetic retinopathy. In this article, we have summarized and critically reviewed the pathophysiological role of Ang-1-Tie2 signalling pathway.