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171.
Inhibition of neutrophil priming and tyrosyl phosphorylation by cepharanthine, a nonsteroidal antiinflammatory drug. 总被引:1,自引:0,他引:1
Receptor-mediated superoxide (O2.-)-generation and tyrosyl phosphorylation of neutrophil proteins, such as 58, 65, 84, 108 and 115 kDa, were enhanced by priming cells with granulocyte colony stimulating factor (G-CSF) [Akimura, K. et al. Arch. Biochem. Biophys. 298: 703-709, 1992]. To elucidate the possible involvement of tyrosyl phosphorylation of neutrophil proteins in the enhancing mechanism of O2.- generation, the effect of cepharanthine, a biscoclaurine alkaloid that inhibits phorbol 12-myristate 13-acetate (PMA)- and receptor-mediated O2.- generation, on the priming of human peripheral neutrophils (HPPMN) was studied. Both enhancement of formyl-methionyl-leucyl- phenylalanine (FMLP)-mediated O2.- generation and tyrosyl phosphorylation of some neutrophil proteins, i.e., 115, 108 and 84 kDa proteins, by HHPMN after treatment with G-CSF were strongly inhibited by cepharanthine in a concentration- and treatment-time-dependent manner. In contrast, inhibition of PMA-mediated O2.- generation by cepharanthine was weak and independent of treatment time. These results suggest that cepharanthine might inhibit the priming step of neutrophil activation concomitantly with its inhibition of the tyrosyl phosphorylation of some neutrophil proteins that might underlie the mechanism for priming of neutrophils with G-CSF. 相似文献
172.
柴达木盆地荒漠土壤蓝藻群落的初步研究 总被引:6,自引:0,他引:6
本文分析了柴达木盆地东部和中部具有代表性地区的丘陵、戈壁和沙丘的蓝藻种类组成、生物量及主要的土壤化学成分;采用了模糊聚类、系统聚类及多元线性回归等方法分析藻类的群落及其与环境因子的关系。共鉴定出21种蓝藻,其中6种为国内首次报道。研究表明:土壤含磷量、总盐量及与粘性和湿度有关的土壤结构是决定柴达木盆地蓝藻群落组成的重要因素。 相似文献
173.
Complete congruence between morphological and rbcL-based molecular phylogenies in birches and related species (Betulaceae). 总被引:2,自引:0,他引:2
Estimations of phylogenies from morphological and molecular data often show contrasting results. We compared morphological and molecular phylogenies in an ancient family of woody dicots, the Betulaceae (birch family). The phylogeny of the family was estimated from parsimony analysis of morphological characters in the genera Alnus, Betula, Carpinus, Corylus, Ostrya, and Ostryopsis and from parsimony and distance-matrix analyses of DNA sequences of the chloroplast gene encoding the large subunit of ribulose-1,5-biphosphate carboxylase (rbcL) in the genera Alnus, Betula, Carpinus, Corylus, and Ostrya and in two outgroups, Quercus and Liquidambar. The topologies obtained by the different methods were completely congruent, and bootstrapping strongly supported the division of the family Betulaceae into two major clades, Betuleae (Alnus and Betula) and Coryleae (other members). Only slightly more homoplasy was present in the rbcL sequence data set than in the morphological set. Relative-rate tests indicated that the Coryleae clade had a faster rate of rbcL evolution than did the Betuleae clade. Heterogeneity of rates of morphological evolution also paralleled those for rbcL. 相似文献
174.
Atomic force microscopy of uncoated plasmid DNA: nanometer resolution with only nanogram amounts of sample. 总被引:1,自引:0,他引:1
M Q Li H G Hansma J Vesenka G Kelderman P K Hansma 《Journal of biomolecular structure & dynamics》1992,10(3):607-617
Reproducible, high-contrast, nanometer-resolution AFM images of uncoated plasmid DNA can be obtained with nanogram quantities of DNA with the help of two advances in sample preparation: (1) Heating a DNA solution at 35 degrees C for 10 to 20 minutes before deposition on mica helps separate and spread the DNA, and (2) Using 5 microliter drops of the heated DNA solution in the concentration range of 2 to 10 nanogram/microliter in contact with a specially prepared mica surface for 5 to 10 minutes gives optimal coverage with only nanograms of DNA. 相似文献
175.
Statistical properties of bootstrap estimation of phylogenetic variability from nucleotide sequences. I. Four taxa with a molecular clock. 总被引:11,自引:0,他引:11
The statistical properties of sample estimation and bootstrap estimation of phylogenetic variability from a sample of nucleotide sequences are studied by using model trees of three taxa with an outgroup and by assuming a constant rate of nucleotide substitution. The maximum-parsimony method of tree reconstruction is used. An analytic formula is derived for estimating the sequence length that is required if P, the probability of obtaining the true tree from the sampled sequences, is to be equal to or higher than a given value. Bootstrap estimation is formulated as a two-step sampling procedure: (1) sampling of sequences from the evolutionary process and (2) resampling of the original sequence sample. The probability that a bootstrap resampling of an original sequence sample will support the true tree is found to depend on the model tree, the sequence length, and the probability that a randomly chosen nucleotide site is an informative site. When a trifurcating tree is used as the model tree, the probability that one of the three bifurcating trees will appear in > or = 95% of the bootstrap replicates is < 5%, even if the number of bootstrap replicates is only 50; therefore, the probability of accepting an erroneous tree as the true tree is < 5% if that tree appears in > or = 95% of the bootstrap replicates and if more than 50 bootstrap replications are conducted. However, if a particular bifurcating tree is observed in, say, < 75% of the bootstrap replicates, then it cannot be claimed to be better than the trifurcating tree even if > or = 1,000 bootstrap replications are conducted. When a bifurcating tree is used as the model tree, the bootstrap approach tends to overestimate P when the sequences are very short, but it tends to underestimate that probability when the sequences are long. Moreover, simulation results show that, if a tree is accepted as the true tree only if it has appeared in > or = 95% of the bootstrap replicates, then the probability of failing to accept any bifurcating tree can be as large as 58% even when P = 95%, i.e., even when 95% of the samples from the evolutionary process will support the true tree. Thus, if the rate-constancy assumption holds, bootstrapping is a conservative approach for estimating the reliability of an inferred phylogeny for four taxa. 相似文献
176.
Mitochondrial DNA from the fall armyworm, Spodoptera frugiperda (J.E. Smith), was cloned and characterized using restriction enzyme mapping. Genome size is approximately 16.3 kilobase (Kb), consistent with that of most animals. Three fragments, 8.1 Kb, 6.2 Kb, and 2.0 Kb, were produced by digestion with restriction enzyme Xbal and cloned into a pUC19 vector. Twenty-nine restriction enzymes were used to generate a detailed physical restriction enzyme map of the three cloned fragments. These data represent the first detailed characterization of a lepidopteran mitochondrial genome. © 1992 Wiley-Liss, Inc. 相似文献
177.
Desmosomes, complex multisubunit structures that assemble at sites of cell-cell contact, are important components of the epithelial junctional complex. Desmosome assembly requires the coordinated interaction at the plasma membrane of at least 8 cytoplasmic and integral membrane proteins organized into two structurally and functionally distinct domains, the cytoplasmic plaque and membrane core. Previous studies (Pasdar et al., J. Cell Biol., 113:645-655) provided evidence that cytokeratin filaments and microtubules may regulate transfer and assembly of cytoplasmic plaque and membrane core proteins, respectively. To determine directly the role of microtubules in these processes, Madin-Darby canine kidney (MDCK) cells were treated with nocodazole or colchicine to disrupt the microtubular network. Biochemical analysis of the different components of the cytoplasmic plaque and membrane core domains revealed little or no effect of nocodazole or colchicine on the kinetics of synthesis, post-translational modifications, transfer of proteins to the plasma membrane or their metabolic stability in the presence or absence of cell-cell contact. Likewise, immunofluorescence analysis of desmosome formation demonstrated an apparently normal desmosome assembly in the presence of nocodazole or colchicine upon induction of cell-cell contact. These results indicate that an intact microtubular network is not necessary for the processing or transport of the desmosomal membrane core glycoproteins to the plasma membrane in the absence or presence of cell-cell contact. Furthermore, the integration of the cytoplasmic plaque and membrane core domains induced by cell-cell contact at the plasma membranes of adjacent cells does not require the presence of functional microtubules. 相似文献
178.
Assignment of genes encoding a unique cytokine (IL12) composed of two unrelated subunits to chromosomes 3 and 5. 总被引:14,自引:0,他引:14
D Sieburth E W Jabs J A Warrington X Li J Lasota S LaForgia K Kelleher K Huebner J J Wasmuth S F Wolf 《Genomics》1992,14(1):59-62
IL12 (formerly NKSF or CLMF) is a unique cytokine composed of two unrelated disulfide-linked subunits. The larger 40-kDa subunit (p40) is a member of the cytokine receptor family, and the smaller 35-kDa subunit (p35) is related to IL6 and GCSF. The chromosomal localization of these two subunits was determined by PCR analysis of DNA from rodent-human hybrids. More refined mapping was obtained by PCR analysis of hybrids containing translocation chromosomes and for p40, by analysis of radiation hybrids. The subunits map to different chromosomes: p40 (IL12B) to 5q31-q33 and p35 (IL12A) to 3p12-3q13.2. 相似文献
179.
Human dopamine transporter gene (DAT1) maps to chromosome 5p15.3 and displays a VNTR. 总被引:24,自引:0,他引:24
D J Vandenbergh A M Persico A L Hawkins C A Griffin X Li E W Jabs G R Uhl 《Genomics》1992,14(4):1104-1106
The human dopamine transporter (DAT1) gene is localized to chromosome 5p15.3 by in situ hybridization and PCR amplification of rodent somatic cell hybrid DNA. Analysis of a 40-bp repeat in the 3' untranslated region of the message revealed variable numbers of the repeat ranging from 3 to 11 copies. These results will aid in the investigation of a role for this gene in genetic disorders of the dopaminergic system in humans. 相似文献
180.
Recently we isolated a cellular DNA binding protein, designated interleukin enhancer binding factor (ILF), that binds to purine-rich regulatory motifs in both the HIV-1 LTR and the IL2 promoter. Further analysis of the ILF gene reveals the existence of two mRNA species, both of which encode proteins containing the recently described fork head DNA binding domain. Gel retardation analysis demonstrates that the portion of the ILF protein with homology to the fork head domain is sufficient to mediate DNA binding to a number of related purine-rich sequences. ILF mRNA is expressed constitutively in both lymphoid and nonlymphoid tissues. Chromosomal mapping localizes the ILF gene to human chromosome 17q25, which is a site of chromosomal translocations in some cases of human acute myelogous leukemias. These studies further characterize the structure of the cellular DNA binding protein ILF and may prove valuable in the molecular analysis of possible translocations affecting this gene. 相似文献