Poliovirus mutants resistant to neutralization with soluble cell receptors

Poliovirus mutants resistant to neutralization with soluble cellular receptor were isolated. Replication of soluble receptor-resistant (srr) mutants was blocked by a monoclonal antibody directed against the HeLa cell receptor for poliovirus, indicating that the mutants use this receptor to enter cells. The srr mutants showed reduced binding to HeLa cells and cell membranes. However, the reduced binding phenotype did not have a major impact on viral replication, as judged by plaque size and one-step growth curves. These results suggest that the use of soluble receptors as antiviral agents could lead to the selection of neutralization-resistant mutants that are able to bind cell surface receptors, replicate, and cause disease.     

缺氧诱导因子和促红细胞生成素及其受体基因在绵羊各组织中表达量

【目的】研究缺氧诱导因子(HIF)及其下游靶基因促红细胞生成素(EPO)及其受体(EPOR)在绵羊正常生理状况下各组织的表达,为靶向调控或缓解绵羊缺氧应激的研究提供组织学依据。【方法】采用实时荧光定量PCR方法,检测4只新疆细毛羊14种组织中HIF、EPO和EPOR基因的相对表达量。【结果】HIF-1α和HIF-2α基因均在绵羊肺组织的相对表达量最高,且极显著高于其它组织(P<0.01);在肺脏HIF-2α基因的表达量约为HIF-1α表达量的5.2倍。EPO基因在绵羊肾脏的相对表达量最高且显著高于垂体、结肠、脾脏、盲肠、肝脏、肾上腺、瘤胃、下丘脑以及心脏(P<0.05)。EPOR基因在肺脏的表达量最高,肺脏和睾丸的相对表达量显著高于脾脏、下丘脑、肾脏、心脏等组织(P<0.05)。【结论】HIF-1α、HIF-2α和EPO及其受体基因在绵羊的肺部或肾脏的高表达,可能是绵羊缺氧应激感受及其调控的重要器官。     

Little evidence for developmental plasticity of adult hematopoietic stem cells

To rigorously test the in vivo cell fate specificity of bone marrow (BM) hematopoietic stem cells (HSCs), we generated chimeric animals by transplantation of a single green fluorescent protein (GFP)-marked HSC into lethally irradiated nontransgenic recipients. Single HSCs robustly reconstituted peripheral blood leukocytes in these animals, but did not contribute appreciably to nonhematopoietic tissues, including brain, kidney, gut, liver, and muscle. Similarly, in GFP+:GFP- parabiotic mice, we found substantial chimerism of hematopoietic but not nonhematopoietic cells. These data indicate that "transdifferentiation" of circulating HSCs and/or their progeny is an extremely rare event, if it occurs at all.     

Regulation of expression of the interleukin-2 receptor on hematopoietic cells by interleukin-3

Remarkable similarities in the intracellular and genetic events occur when lymphoid and hematopoietic cells are exposed to their specific growth factors. The interleukin-2 (IL-2) receptor, whose cell-surface expression is an absolute requirement for the growth and differentiation of lymphoid cells, was detected on various nonlymphoid hematopoietic cell types in this study. Cell lines consisting either of granulocyte-macrophage precursors or mast cells, which are dependent on interleukin-3 (IL-3) for their growth, expressed high levels of the IL-2 receptor on their surface. Analysis of the binding characteristics of these receptors with 125I-labeled recombinant IL-2 revealed that only receptors with low affinity for IL-2 were present on these cells. Addition of purified recombinant IL-3 to these cell lines led to an increase in IL-2 receptor gene expression within 1 hour in isolated nuclei. This IL-3--induced increase in the number of IL-2 receptors on the cell surface is maximal within 24 hours. Addition of 10,000 units of IL-2 to these cells had no apparent effect on their growth or differentiation. The presence of the receptor with only low affinity for IL-2 on hematopoietic cells and the regulation by IL-3 suggest that this receptor is involved in some important metabolic event in hematopoiesis.     

消化道肿瘤贫血患者促红细胞生成素与贫血治疗方案的关系

目的分析消化道肿瘤患者内源性促红细胞生成素水平及贫血状态,探讨使用重组人促红细胞生成素治疗消化道肿瘤相关性贫血的方案.方法内源性促红细胞生成素采用Elisa检测,血红蛋白采用常规检测.消化道肿瘤非贫血患者为对照组,消化道肿瘤贫血患者组为观察组.结果统计发现男女之间的贫血率没有差异,消化道肿瘤相关性贫血患者占38.95%,其中以胃癌居首,占42.2%,食管鳞癌最低,占35.6%.消化道肿瘤患者在化疗前贫血比非贫血患者EPO高而Hb低,两者存在逆相关关系,化疗后贫血患者Hb继续降低,EPO上升;而在化疗后非贫血患者中出现的26例贫血患者,其中16例出现EPO急剧上升,10例EPO几乎不变,EPO存在极显著差异,具有统计学意义,而Hb没有明显的差异.结论消化道肿瘤相关性贫血发生率较高,在临床治疗中要密切关注.     

An agonist of toll-like receptor 5 has radioprotective activity in mouse and primate models

The toxicity of ionizing radiation is associated with massive apoptosis in radiosensitive organs. Here, we investigate whether a drug that activates a signaling mechanism used by tumor cells to suppress apoptosis can protect healthy cells from the harmful effects of radiation. We studied CBLB502, a polypeptide drug derived from Salmonella flagellin that binds to Toll-like receptor 5 (TLR5) and activates nuclear factor-kappaB signaling. A single injection of CBLB502 before lethal total-body irradiation protected mice from both gastrointestinal and hematopoietic acute radiation syndromes and resulted in improved survival. CBLB502 injected after irradiation also enhanced survival, but at lower radiation doses. It is noteworthy that the drug did not decrease tumor radiosensitivity in mouse models. CBLB502 also showed radioprotective activity in lethally irradiated rhesus monkeys. Thus, TLR5 agonists could potentially improve the therapeutic index of cancer radiotherapy and serve as biological protectants in radiation emergencies.     

EGF receptor and erbB-2 tyrosine kinase domains confer cell specificity for mitogenic signaling

The epidermal growth factor (EGF) receptor (EGFR) can efficiently couple with mitogenic signaling pathways when it is transfected into interleukin-3 (IL-3)-dependent 32D hematopoietic cells. When expression vectors for erbB-2, which is structurally related to EGFR, or its truncated counterpart, delta NerbB-2, were introduced into 32D cells, neither was capable of inducing proliferation. This was despite overexpression and constitutive tyrosine kinase activity of their products at levels associated with potent transformation of fibroblast target cells. Thus, EGFR and erbB-2 couple with distinct mitogenic signaling pathways. The region responsible for the specificity of intracellular signal transduction was localized to a 270-amino acid stretch encompassing their respective tyrosine kinase domains. Thus, tissue- or cell-specific regulation of growth factor receptor signaling can occur at a point after the initial interaction of growth factor with receptor. Such specificity in signal transduction may account for the selection of certain oncogenes in some malignancies.     

花青素代谢对陆地棉叶片和纤维色泽呈现的影响

【目的】棉花作为一种重要的经济作物和油料作物,其叶片和纤维均可积累色素物质,呈现不同颜色。叶绿素、类胡萝卜素和花青素的含量及其比例是棉花叶片呈色的主要原因,而棕色纤维中主要色素成分为花青素单体氧化聚合而成的原花青素及其衍生物。通过分析陆地棉不同的叶色突变体叶片和纤维中的花青素含量,花青素和原花青素合成途径中关键基因的表达,探究棉花叶片和纤维颜色呈现与花青素合成的关系,为叶色突变体的利用和彩色棉纤维色泽的改良奠定基础。【方法】通过测定21个陆地棉叶色突变体的叶片花青素含量,根据叶色突变体叶片、纤维颜色和花青素含量差异,筛选了其中6个典型的棉花叶色突变体作为研究材料,比较叶片和纤维（开花后15 d）中的花青素含量,分析花青素含量与叶片、纤维颜色呈现的关系;同时检测叶片及不同发育时期纤维（开花后5、10、15和20 d）中花青素合成关键基因GhCHS和原花青素合成途径关键基因GhLAR和GhANR的表达水平,分析目标基因对叶片和纤维颜色呈现的影响。【结果】21个陆地棉叶色突变体叶片中的花青素含量差异显著,呈现紫红色或紫色的叶片花青素含量高。在筛选的6个陆地棉叶色突变体及其对照叶片和不同发育时期纤维中,叶片花青素含量显著高于纤维,棕色纤维的花青素含量显著高于白色纤维。叶片中,GhCHS表达量较高,而GhANR和GhLAR表达量较低,花青素积累与颜色呈现与其表达量没有显著的相关性;而在纤维中,GhANR和GhLAR在棕色纤维的表达量极显著高于白色纤维中,且主要集中在纤维发育的5—15 DPA高表达。【结论】陆地棉叶片和纤维的颜色呈现均与花青素含量有关,紫色及紫红色叶片以及棕色纤维中花青素含量高,但纤维颜色的形成与棉花叶片颜色呈现没有显著的相关性,其花青素含量与原花青素合成途径的关键基因GhANR和GhLAR表达水平直接相关,表明棉花叶片和纤维中的呈色机制不一致,原花青素主要在纤维中积累显色。     

Tumor formation dependent on proteoglycan biosynthesis

The role proteoglycans play in tumor formation was examined by measuring the tumorigenicity of proteoglycan-deficient Chinese hamster ovary cell mutants in nude mice. When 10(7) cells were injected subcutaneously, mutants with less than about 15% of the wild-type level of proteoglycan synthesis did not produce tumors. Mutants defective in the synthesis of heparan sulfate proteoglycans also did not form tumors, whereas mutants with altered chondroitin sulfate proteoglycans were tumorigenic. Tumors arose from mixtures of wild-type and nontumorigenic mutant cells and contained both cell types, suggesting that wild-type cell proteoglycans enabled mutant cells to survive. The failure of heparan sulfate-deficient mutants to form tumors depended on the ability of the host to mount a B cell-mediated immune reaction.     

The effect of histone gene deletions on chromatin structure in Saccharomyces cerevisiae

As a way of studying nucleosome assembly and maintenance in Saccharomyces cerevisiae, mutants bearing deletions or duplications of the genes encoding histones H2A and H2B were analyzed. Previous genetic analysis had shown that only one of these mutants exhibited dramatic and pleiotropic phenotypes. This mutant was also the only one that contained disrupted chromatin, suggesting that the original phenotypes were attributable to alterations in chromosome structure. The chromatin disruption in the mutant, however, did not extend over the entire genome, but rather was localized to specific regions. Thus, while the arrangement of nucleosomes over the HIS4 and GAL1 genes, the telomeres, and the long terminal repeats (delta sequences) of Ty retrotransposons appeared essentially normal, nucleosomes over the CYH2 and UBI4 genes and the centromere of chromosome III were dramatically disrupted. The observation that the mutant exhibited localized chromatin disruptions implies that the assembly or maintenance of nucleosomes differs over different parts of the yeast genome.     

The slit receptor EVA-1 coactivates a SAX-3/Robo mediated guidance signal in C. elegans

The SAX-3/roundabout (Robo) receptor has SLT-1/Slit-dependent and -independent functions in guiding cell and axon migrations. We identified enhancer of ventral-axon guidance defects of unc-40 mutants (EVA-1) as a Caenorhabditis elegans transmembrane receptor for SLT-1. EVA-1 has two predicted galactose-binding ectodomains, acts cell-autonomously for SLT-1/Slit-dependent axon migration functions of SAX-3/Robo, binds to SLT-1 and SAX-3, colocalizes with SAX-3 on cells, and provides cell specificity to the activation of SAX-3 signaling by SLT-1. Double mutants of eva-1 or slt-1 with sax-3 mutations suggest that SAX-3 can (when slt-1 or eva-1 function is reduced) inhibit a parallel-acting guidance mechanism, which involves UNC-40/deleted in colorectal cancer.     

EMS诱变谷子‘长农35号’突变体成熟期株型的鉴定与分析

[目的]建立谷子突变体库,以便在谷子分子生物学研究中应用。[方法]以生产上主要推广种植的谷子品种‘长农35号’干种子为实验材料,采用0.8%和1.0%甲磺酸乙酯（EMS）进行了诱变处理,并对所得突变体成熟期株型的7个表型形状进行考察,并据此对突变体进行分类。[结果]试验共收获株型相关的M1代突变体材料共282份,其中,0.8%EMS诱变‘长农35号’获得株型突变体材料100个单株,可分为10个组;1.0%EMS诱变‘长农35号’获得株型突变体材料182个单株,可分为17个组。M1代成熟期株型相关性状突变体分析结果表明：1.0%EMS处理‘长农35号’所获突变体,在株高、穗下节粗、穗下第一节间粗和茎节数4个性状与对照有显著差异,而0.8%处理与对照差异不显著。[结论]对于‘长农35号’来讲,采用1.0%EMS进行诱变处理更有利于多类型大量突变单株的获得。     

Transformation by v-sis occurs by an internal autoactivation mechanism

Transformation by the v-sis oncogene appears to require an interaction of its protein product, p28v-sis, with the receptor for the platelet-derived growth factor (PDGF). However, this interaction may not occur at the cell surface as predicted by the autocrine hypothesis because phenotypic transformation was not reversed by incubation of SSV-NRK cells with antisera to PDGF and because morphological transformation did not occur when nontransformed NRK cells were cultured continuously with p28v-sis. A mutant of the wild-type v-sis gene was constructed that encodes a v-sis protein targeted for retention within the endoplasmic reticulum and Golgi. NRK cells expressing the mutant v-sis gene did not secrete any detectable v-sis protein but were as fully transformed as wild-type v-sis transfectants. The results support a mechanism of transformation by v-sis in which internal activation of the PDGF receptor occurs before expression of either p28v-sis or the PDGF receptor at the cell surface.     

Three-dimensional structure of the LDL receptor-binding domain of human apolipoprotein E

Human apolipoprotein E, a blood plasma protein, mediates the transport and uptake of cholesterol and lipid by way of its high affinity interaction with different cellular receptors, including the low-density lipoprotein (LDL) receptor. The three-dimensional structure of the LDL receptor-binding domain of apoE has been determined at 2.5 angstrom resolution by x-ray crystallography. The protein forms an unusually elongated (65 angstroms) four-helix bundle, with the helices apparently stabilized by a tightly packed hydrophobic core that includes leucine zipper-type interactions and by numerous salt bridges on the mostly charged surface. Basic amino acids important for LDL receptor binding are clustered into a surface patch on one long helix. This structure provides the basis for understanding the behavior of naturally occurring mutants that can lead to atherosclerosis.     

孕牛血清中可溶性白细胞介素2受体水平的变化

应用酶标双搞体夹心法分别测定未孕牛、妊娠早期（＜１００ｄ）、妊娠中期（１００～２００ｄ）和妊娠后期（＞２００ｄ）的黑白花奶牛各１０头的血清可溶性白细胞介素２受体水平的变化，结果表明，不同妊娠阶段各组与未孕牛差异不显著（Ｐ＞０．０５），这就说明了妊娠时母体外周血清中１Ｌ－２Ｒ阳性表达细胞无显著变化，从而抑制机体对胚胎或胎儿的排斥反应     

Zinc mediation of the binding of human growth hormone to the human prolactin receptor

Human growth hormone (hGH) elicits a diverse set of biological activities including lactation that derives from binding to the prolactin (PRL) receptor. The binding affinity of hGH for the extracellular binding domain of the hPRL receptor (hPRLbp) was increased about 8000-fold by addition of 50 micromolar ZnCl2. Zinc was not required for binding of hGH to the hGH binding protein (hGHbp) or for binding of hPRL to the hPRLbp. Other divalent metal ions (Ca2+, Mg2+, Cu2+, Mn2+, and Co2+) at physiological concentrations did not support such strong binding. Scatchard analysis indicated a stoichiometry of one Zn2+ per hGH.hPRLbp complex. Mutational analysis showed that a cluster of three residues (His18, His21, and Glu174) in hGH and His188 from the hPRLbp (conserved in all PRL receptors but not GH receptors) are probable Zn2+ ligands. This polypeptide hormone.receptor "zinc sandwich" provides a molecular mechanism to explain why nonprimate GHs are not lactogenic and offers a molecular link between zinc deficiency and its association with altered functions of hGH.     

Intracistron Recombination in the Wx/wx Region in Maize

Five independently occurring waxy (wx) mutants produce low frequencies of standard type (Wx) pollen grains (0.3 to 3.8 x 10(-5)). In crosses between these mutants, frequencies of Wx pollen grains range from 1.4 to 88 x 10(-5), depending on the cross. Data from the crosses allow the ordering of the mutants within the region. Functional complementation between the different mutants does not occur.