LBL, a novel, developmentally regulated, laminin-binding lectin.

A 190/220-kDa complex found in integrin preparations was purified, and monoclonal antibodies were raised against it. The immunoaffinity-purified complex appears to be a trimer of very similar or identical 70-kDa subunits. It is a novel extracellular matrix molecule as determined by its subunit composition, N-terminal amino acid sequence, and in vivo localization. It is distributed widely in basement membranes including those from muscle, nerve, and kidney. It is also present in connective tissue regions such as perineurium and perimysium. It has the unusual property that it is initially expressed very late in avian development near the time of hatching. This protein is found to copurified with integrin because it binds to the carbohydrate support in Sepharose. Hemagglutination assays with mono- and disaccharides show that it functions as a lectin with galactoside-binding specificity. This protein is also found to bind strongly and specifically to laminin at a site distinct from its lectin activity, but does not bind to fibronectin or type IV collagen. The protein appears to be conserved and is a common contaminant of many laminin preparations. We call this novel protein "LBL" for laminin-binding lectin.     

Structural diversity in the extracellular faces of peptidergic G-protein-coupled receptors. Molecular cloning of the mouse C5a anaphylatoxin receptor.

The mouse C5a receptor gene was isolated using the human C5a receptor cDNA probe recently described (Gerard, N. P., and C. Gerard. 1991. Nature 349:614). By analogy with the human gene, the mouse homolog contains two exons with the 5' untranslated region and initiating methionine codon present in exon 1 and the remainder of the molecule in exon 2. Generation of an expressible cDNA for the mouse C5a receptor was accomplished using the polymerase chain reaction and a sense oligodeoxynucleotide primer which included an initiation codon just 5' to the sequence encoding the N-linked glycosylation site. When transfected into human 293 kidney epithelial cells the cloned cDNA directs expression of a binding site for human C5a anaphylatoxin with a binding constant of 2.5 +/- 0.3 nM; the human C5a receptor expressed under identical conditions has a Kd of 1.7 +/- 0.2 nM. Overall, the deduced amino acid sequences of the receptors are 65% identical given the analogous gene structures. Alignment of the sequences as seven transmembrane segment receptors reveals that the greatest structural diversity (approximately 70%) exists in the putative extracellular domains. In contrast, species differences among other members of this family of seven membrane-spanning receptors is generally only 10 to 20%, even for receptors whose ligands are relatively small and not expected to interact with sites on the extracellular surfaces. A high degree of structural identify is observed for the C5a receptors in the transmembrane segments and in all but one of the loops predicted to exist in the cytoplasm. Inasmuch as critical structures responsible for high affinity binding of the 74 amino acid polypeptide to both C5a receptors involve features conserved between species, these data provide the starting point for mutagenesis studies to determine the nature of the binding and activation sites for the chemotactic receptors. Additionally, these data provide a reagent for immunologic and molecular genetic studies on the role of C5a receptors in inflammatory models.     

THE INFLUENCE OF WATER STRESS ON STEM AND LEAF PHOTOSYNTHESIS IN GLYCINE MAX AND SPARTEUM JUNCEUM (LEGUMINOSAE)

Stem and leaf photosynthesis were measured in Glycine max var. essex (soybean) and Sparteum junceum (Spanish broom). The significance of stem photosynthesis to whole plant growth was evaluated by blocking stem photosynthesis with black straw sections. The growth of S. junceum was reduced by 18% when black straws were used in comparison to clear straws. The whole plant growth of G. max was not influenced by blocking the stem carbon contribution. Mean midday leaf photosynthesis was 12 μmol CO₂ m^–2 s^–1 and 17 μmol CO₂ m^–2 s^–1 for G. max and 5. junceum, respectively. Mean midday stem photosynthesis of S. junceum was 6.5 μmol CO₂ m^–2 s^–1; however, positive net photosynthesis did not occur in G. max stems. Water stress caused a proportionally greater decrease in leaf photosynthesis compared to that of stems during diurnal cycles of photosynthesis in S. junceum. As a result the contribution to canopy carbon gain by stem photosynthesis increased from 38% to 48% of the total plant carbon gain under reduced water availability.     

The novel type II toxin–antitoxin PacTA modulates Pseudomonas aeruginosa iron homeostasis by obstructing the DNA-binding activity of Fur

Type II toxin–antitoxin (TA) systems are widely distributed in bacterial and archaeal genomes and are involved in diverse critical cellular functions such as defense against phages, biofilm formation, persistence, and virulence. GCN5-related N-acetyltransferase (GNAT) toxin, with an acetyltransferase activity-dependent mechanism of translation inhibition, represents a relatively new and expanding family of type II TA toxins. We here describe a group of GNAT-Xre TA modules widely distributed among Pseudomonas species. We investigated PacTA (one of its members encoded by PA3270/PA3269) from Pseudomonas aeruginosa and demonstrated that the PacT toxin positively regulates iron acquisition in P. aeruginosa. Notably, other than arresting translation through acetylating aminoacyl-tRNAs, PacT can directly bind to Fur, a key ferric uptake regulator, to attenuate its DNA-binding affinity and thus permit the expression of downstream iron-acquisition-related genes. We further showed that the expression of the pacTA locus is upregulated in response to iron starvation and the absence of PacT causes biofilm formation defect, thereby attenuating pathogenesis. Overall, these findings reveal a novel regulatory mechanism of GNAT toxin that controls iron-uptake-related genes and contributes to bacterial virulence.     

口蹄疫病毒非结构蛋白3AB双抗体夹心ELISA方法的建立

抗原纯净度是口蹄疫(Foot-and-mouthdisease,FMD)灭活疫苗质量检验的一项重要内容,一般采用疫苗2–3次免疫动物后,检测非结构蛋白(Non-structuralprotein,NSP)抗体是否阳转,判断疫苗抗原的纯净度。文中旨在建立定量检测FMD灭活疫苗抗原中NSP3AB含量的ELISA方法,为疫苗质量控制提供参考方法。利用口蹄疫病毒(Foot-and-mouthdiseasevirus,FMDV)NSP3A单克隆抗体和辣根过氧化物酶(Horseradish peroxidase,HRP)标记的3B单克隆抗体,建立定量检测NSP3AB含量的双抗体夹心ELISA检测方法。采用原核表达并纯化的3AB蛋白作为标准品,标准品系列稀释,绘制标准曲线,以标准品与未加抗原的阴性对照吸光值(OD)的比值大于2.0的标准品最低浓度为最低检测限。标准品浓度介于4.7–600.0 ng/mL之间时,测得的OD值与浓度呈线性相关,回归曲线呈直线,相关系数R2=0.99,确定最低检测限为4.7ng/mL。检测12份未纯化灭活抗原中3AB蛋白含量介于9.3–200.0ng/mL之间;而纯化后的...     

大花三色堇育种研究进展

该文概括总结了目前国内外有关大花三色堇(Viola × wittrockiana Gams.)的种质资源、主要性状遗传改良和育种技术等方面的研究进展。大花三色堇品种丰富, 且近缘种众多; 国内外对大花三色堇的主要观赏性状、营养性状及抗性等的遗传与改良进行了较为细致的研究; 通过采用杂交育种、多倍体育种、诱变育种和组织培养等技术取得了众多研究成果。雄性不育、花色花斑遗传规律和生物技术成为大花三色堇育种研究的工作重点。我国今后应在保护和利用其种质资源的基础上, 加快对大花三色堇新品种的培育。     

Inhibition of mitochondrial complex I improves glucose metabolism independently of AMPK activation

Accumulating evidences showed metformin and berberine, well‐known glucose‐lowering agents, were able to inhibit mitochondrial electron transport chain at complex I. In this study, we aimed to explore the antihyperglycaemic effect of complex I inhibition. Rotenone, amobarbital and gene silence of NDUFA13 were used to inhibit complex I. Intraperitoneal glucose tolerance test and insulin tolerance test were performed in db/db mice. Lactate release and glucose consumption were measured to investigate glucose metabolism in HepG2 hepatocytes and C2C12 myotubes. Glucose output was measured in primary hepatocytes. Compound C and adenoviruses expressing dominant negative AMP‐activated protein kinase (AMPK) α1/2 were exploited to inactivate AMPK pathway. Cellular NAD⁺/NADH ratio was assayed to evaluate energy transforming and redox state. Rotenone ameliorated hyperglycaemia and insulin resistance in db/db mice. It induced glucose consumption and glycolysis and reduced hepatic glucose output. Rotenone also activated AMPK. Furthermore, it remained effective with AMPK inactivation. The enhanced glycolysis and repressed gluconeogenesis correlated with a reduction in cellular NAD⁺/NADH ratio, which resulted from complex I suppression. Amobarbital, another representative complex I inhibitor, stimulated glucose consumption and decreased hepatic glucose output in vitro, too. Similar changes were observed while expression of NDUFA13, a subunit of complex I, was knocked down with gene silencing. These findings reveal mitochondrial complex I emerges as a key drug target for diabetes treatment. Inhibition of complex I improves glucose homoeostasis via non‐AMPK pathway, which may relate to the suppression of the cellular NAD⁺/NADH ratio.     

内蒙古库布齐沙地黑线仓鼠食物构成的季节变化

黑线仓鼠 (Ｃｒｉｃｅｔｕｌｕｓｂａｒａｂｅｎｓｉｓ)是广泛分布于我国华北和中原地区草原、农田的一种农牧业害鼠[8] ,在这些生境中 ,其食物以各种农作物和牧草种子为主 ,并取食大量昆虫[1,3 ,5,6 ] 。在鄂尔多斯高原库布齐沙地环境中 ,由于该种耐受高温环境的能力相对较低 ,仅分布在郁蔽程度较高的固定沙地和农田。研究表明 ,本地区该种的数量近年呈上升趋势[2 ] 。结合研究其数量变动规律 ,我们于 1996年 4～ 10月对其食物构成的季节变化进行了研究 ,以分析其生态适应对策。1　研究方法研究点设在库布齐沙地东段的中国农业科学院草原研…     

应用环磷酰胺研制细胞表面抗原的单克隆抗体

利用环磷酰胺和杂交瘤技术 ,成功制备了 1株稳定分泌抗人CD80 分子单克隆抗体的杂交瘤细胞。实验结果表明 ,该单抗腹水效价为 1 0 6 ,属IgG1亚类 ,特异性强 ,为今后的应用打下了基础。