Cytolytic activity of Ia-restricted T cell clones and hybridomas: evidence for a cytolytic mechanism independent of interferon-gamma, lymphotoxin, and tumor necrosis factor-alpha

Ten different helper T cell (Th) hybridomas that are specific to Ia or antigen plus Ia were found to express nonspecific cytolytic activity toward the cytotoxin (CT)-resistant P815 cells upon activation with either Con A or a monoclonal anti-T3 antibody (T3-mAb). In contrast to cytolytic Th1 clones which secrete high levels of interferon-gamma (IFN-gamma) and cytotoxin (CT) (lymphotoxin (LT, also known as TNF-beta) or tumor necrosis factor-alpha (TNF-alpha], these Th hybridomas produce low or undetectable levels of IFN-gamma and CT. No inhibitory activity of IFN-gamma and CT was observed in culture supernatants of activated Th hybridomas. Double-chamber experiments demonstrated that CT-sensitive L929 cells when physically separated from activated Th1 clones were killed by membrane-permeable CT. Under identical experimental conditions, lysis of P815 cells did not occur. Moreover, activation of Th hybridomas directly in wells containing the CT-sensitive L929 cells failed to induce target cell lysis. This confirms that these Th hybridomas produce little CT and argues against high local concentrations of CT being responsible for Th hybridoma-mediated killing of P815 cells. Finally, a polyclonal rabbit antiserum to rTNF-alpha, which strongly and specifically inhibited CT-mediated and Th1 clone-mediated killing of L929 cells, failed to inhibit P815 lysis by activated Th1 clones and Th hybridomas. These observations establish that a cytolytic mechanism independent of IFN-gamma, LT, and TNF-alpha is responsible for lysis of CT-resistant target cells.     

Effect of pertussis toxin on the heart muscarinic-cholinergic receptors and their function

Administration of pertussis toxin to rats induced a significant increase in heart rate that was evident as soon as 24 hours after the administration of the toxin and that persisted for at least 15 days. Electrical stimulation of the vagus decreased dramatically the heart rate of control animals but was unable to do it so in rats treated with pertussis toxin. In cardiac membranes muscarinic agonists decreased adenylate cyclase activity (approximately equal to 20-25%); no effect was observed in membranes obtained from toxin-treated animals. Agonist displacement of antagonist binding [( 3H] Quinuclidinyl benzilate) indicated that treatment with pertussis toxin decreased the proportion of receptors in the high affinity state for agonists. All these data suggest that blockade of the parasympathetic tone plays a key role in the induction of tachycardia by pertussis toxin.     

卫星影象目视解译方法在湖区植被制图中的应用——以湖南洞庭湖区水域、洲滩植被图为例

植被(包括天然植被、人工植被)作为一种可更新资源始终是遥感应用专家们热心研究的课题。植被分类是植被研究的重要方面之一。利用卫星影象进行植被分类,国内外学者都进行了许多有意义的探索。本文以洞庭湖水域、洲滩植被为对象,试用卫星影象进行植被分类。本文从植被与环境相互依赖关系及在影象上的综合反映出发,提出了影象的景观生态学分析方法;即把影象上色调、形态特征与群落生态学规律结合起来分析,并以此作为植被目视解译的方法。在此基础上,将洞庭湖水域、洲滩划分成五个景观生态模型,17个基本植被类型。     

Synthesis of a nonacosapeptide (beta-fragment) corresponding to the N-terminal sequence 1-29 of human liver metallothionein II and its heavy metal-binding properties

A nonacosapeptide (beta-fragment) corresponding to the N-terminal sequence 1-29 of human liver metallothionein II was synthesized by the fragment condensation method. The Cd-binding ability of the beta-fragment was much stronger than that of cysteine as thionein and synthetic alpha-fragment corresponding to the C-terminal sequence 30-61 of human liver metallothionein II. Both the alpha- and beta-fragments bound preferentially to Cu ions rather than Cd ions.     

Production of human c-myc protein in insect cells infected with a baculovirus expression vector.

A cDNA fragment coding for human c-myc was inserted into the genome of the baculovirus Autographa californica nuclear polyhedrosis virus adjacent to the strong polyhedrin promoter. Insect cells infected with the recombinant virus produced significant amounts of c-myc protein, which constituted the major phosphoprotein component in these cells. By immunoprecipitation and immunoblot analysis, two proteins of 61 and 64 kilodaltons were detected with c-myc-specific antisera. The insect-derived proteins were compared with recombinant human c-myc-encoded proteins synthesized in Escherichia coli and Saccharomyces cerevisiae cells. The c-myc gene product was found predominantly in the nucleus by subcellular fractionation of infected insect cells.     

Clastogen-induced chromosomal breakage as a marker for first trimester prenatal diagnosis of Fanconi anemia

Summary Using cultured trophoblast cells obtained by chorionic villus biopsy, we diagnosed Fanconi anemia (FA) in two pregnancies and excluded it in eight pregnancies at risk for the syndrome. Baseline chromosomal breakage and breakage induced by diepoxybutane (DEB) were analyzed. Increased breakage was used as a marker for the syndrome. Our results were unambiguous and provide a reliable method for prenatal detection of FA in the first trimester of pregnancy.     

Changes in the biological activity of agropyrene on combined application with humus substances in the cultivation ofScenedesmus obliquus (TURP.) krüger

The work is concerned with the question of the effect of humic acids on the biological action of agropyrene, the effective substance from the rootstock of Agropyron repens (L.) P. BEAUV. The test organism was the alga Scenedesmus obliquus (TURP.) KRÜGER, cultivated in mineral solution. The basic biological test was the determination of the number and size of the cells of this alga. It was found that the way in which agropyrene acts on combined application with humus acids depends on which humus fraction is used. It can display a synergic action if humic acid is used, since this substance probably facilitates the penetration of agropyrene into the cells. On the other hand, fulvic acid counteracts the activity of agropyrene and this most probably by mutual binding and blocking of active groups and links.     

脊髓灰质炎病毒中Ⅰ9株基因组克隆及其部分结构分析

以脊髓灰质炎病毒RNA为模板,反转录合成了长链ds-cDNA。将合成的脊灰病毒中I9株ds—cDNA片段重组到质粒pAT153上,获得了约占脊灰病毒中I9基因组95％以上的cDNA克隆。对克隆的中I9cDNA部分片段作了限制性内切酶图谱分析和部分核酸的序列分析,发现脊灰病毒中I9部分核酸顺序有所改变。     

青霉素G酰化酶α亚基Ser177的突变对酶活性的影响

用盒式突变和定点突变对大肠杆菌青霉素G酰化酶α亚基177位ser进行了突变研究,结果发现所挑选的突变体均无酶的活力,这一结果可能可以用来解释Ser 177附近肽段和一些青霉素结合蛋白青霉素结合区在一级结构上保持同源性的原因。     

Early biochemical events after MHC class II-mediated signaling on human B lymphocytes

These studies examined the role of the MHC class II Ag in signal transduction using human B lymphocytes. Early events in signal transduction were considered including the intracellular calcium [Ca2+)i) flux, the activation of phospholipase C, and induction of protein phosphorylation. The (Ca2+)i was enhanced after incubation of B lymphocytes with several mAb anti-HLA class II and cross-linking with rabbit anti-mouse-F(ab')2. We have also demonstrated an enhancement of the (Ca2+)i in response to a suboptimal concentration of a monoclonal anti-IgM either in the presence of or after preincubation with a mAb anti-HLA class II. The activation of phospholipase C was assessed by measuring the generation of inositol phosphates in permeabilized B lymphocytes. mAb anti-HLA-class II of two different epitopes were used to demonstrate both the (Ca2+)i flux and the generation of inositol phosphates. Two-dimensional gel electrophoresis was used to investigate the phosphorylation pattern of resting B lymphocytes and the changes in the pattern after stimulation with soluble mAb anti-HLA-DR, immobilized mAb anti-HLA-DR, and PMA. In addition to the augmentation of phosphorylation observed with regard to phosphoproteins already present in resting B lymphocytes, new phosphorylations were observed after stimulation by any one of the reagents. Furthermore, stimulation by PMA did not result in an identical pattern to that observed after stimulation by mAb anti-HLA class II. An inhibition of the proliferative response to PMA was demonstrated after prestimulation of cells with immobilized mAb anti-HLA-DR, supporting the notion of a shared pathway of activation. In summary, these data demonstrate signal transduction via MHC class II Ag as assessed by three different measures of early events in human B lymphocyte activation and suggest that a protein kinase C pathway is at least partly involved.