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Extrachromosomal circular DNAs in Drosophila melanogaster: Comparison between embryos and Kc0% cells
We established the size distribution of extrachromosomal covalently closed circular DNA molecules from embryos of various Drosophila melanogaster strains and from Kc0% tissue culture cells. In embryos, more than 80% of the circular DNA molecules are smaller than 2.5 kb and all the distributions show a peak of molecules of between 200 and 400 bp. The Kc0% cell distribution differs mainly from that of embryos in that 48% of the molecules have a size between 4 and 8 kb. Correlating with this, circular molecules homologous to copia, 412 and 297 were detected only in Kc0% cells. The three tandemly repeated families containing the 5S genes, the histone genes and the 240 bp repeat of the ribosomal DNA intergenic spacer, which had previously been identified in circular DNAs from embryos, were also found in cultured cells. A fourth tandemly repeated family corresponding to the 1.688 g/cm3 satellite DNA was detected, both in embryos and Kc0% cells. It consists of circular multimeric molecules containing multiple copies of the 359 bp repeated unit. No circular DNA molecules homologous to the actin genes, the type I ribosomal DNA insertion, or the F and I transposable elements were found in embryos or Kc0% cells. Thus it appears that the extrachromosomal circular DNA molecules from embryos and from tissue culture cells differ mainly in the presence of circular copies of the copia-like transposable elements. 相似文献
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Thermophilic hydrogen-oxidizing strains forming round, terminal endospores were isolated from geothermal areas. They were neutrophilic and facultatively autotrophic. They resembledBacillus schlegelii, a thermophilic hydrogen bacterium found so far only in cold environments. Phenotypic similarities, as well as DNA G+C content and DNA:DNA homologies, clearly revealed that the isolated strains belonged to the taxospeciesB. schlegelii. Hence, the strains ofB. schlegelii found in cold environments are probably allochthonous, their origin being geothermal and volcanic areas. 相似文献
4.
Platelet activating factor is a potent stimulant of the production of active oxygen species by human monocyte-derived macrophages 总被引:6,自引:0,他引:6
M Rouis F Nigon M J Chapman 《Biochemical and biophysical research communications》1988,156(3):1293-1301
Platelet activating factor (PAF; C16), 1-O-Hexadecyl-2-acetyl-sn-glycero-3-phosphorylcholine) stimulated the production of active oxygen species by human monocyte-derived macrophages in culture. An optimal response was observed at a concentration of 13 microM PAF with half-maximal stimulation at 5 microM. The generation of superoxide ion (O2-) and hydrogen peroxide (H2O2) in response to PAF was inhibited specifically by a PAF-antagonist (1-O-Hexadecyl-2-acetyl-sn-glycero-3-phospho (N,N,N,-trimethyl) hexanolamine; such generation varied with the degree of maturation of cultured monocytes into macrophages. Production of active oxygen species increased progressively to reach a maximal level between days 4 to 6 of culture and remained maximal to day 12, after which it decreased progressively. Phorbol 12-myristate-13-acetate (PMA) and opsonized zymosan also stimulated generation of O2- and H2O2. PAF was however distinguished by its potent capacity to stimulate O2- and H2O2 production even at late stages of macrophage maturation (18 days), at which time both PMA and zymosan lacked significant effect. These findings suggest that PAF is a factor of potential relevance to the inflammatory role of the macrophage in atherogenesis. 相似文献
5.
P Savatier G Trabuchet C Faure Y Chebloune M Gouy G Verdier V M Nigon 《Journal of molecular biology》1985,182(1):21-29
A 5500 base-pair fragment including the beta-globin gene downstream from codon 122 and about 4000 base-pairs of its 5' flanking sequence was cloned from chimpanzee DNA and thoroughly sequenced before being compared with the corresponding human sequence: 88 point differences (83 substitutions and 5 deletions or insertions of 1 base-pair) were detected as well as seven more important deletion/insertion events. These changes occur preferentially in two kinds of structure. First, 40% of the CpG dinucleotides present in either human or chimpanzee sequences are affected by nucleotide variations. This corresponds to a divergence level considerably higher than that expected. Second, most short repeated sequences found in the 5' extragenic sequence are involved in mutational events (amplification or contraction of the number of basic motifs as well as point substitutions or deletions/insertions of 1 base-pair). Considering the very low level of nucleotide sequence divergence between these two closely related species, our data provide direct evidence for CpG and tandem array instability. 相似文献
6.
Thierry Maillet Annie-Claude Roche Fabienne Thérain Michel Monsigny 《Cancer immunology, immunotherapy : CII》1985,19(3):177-182
Summary In vivo localization of a mouse monoclonal antibody (F2-10.23 IgM) binding leukemic L 1210 cells was studied in DBA/2 mice bearing an L 1210 tumor. F(ab)2 fragments were prepared and their specific binding to L 1210 cells was analyzed by flow cytofluorometry. Radiolocalization studies were performed by using 125I- or 131I-labeled IgM monoclonal antibody or its F(ab')2 fragments to ascertain their capacity to visualize the L 1210 tumor. F(ab)2 fragments were cleared more rapidly than the whole IgM; the clearance was as fast in healthy as in tumor-bearing mice. The tumor-to-muscle ratio observed 24 h after injection of 125I-radiolabeled F(ab)2 fragments and 125I-radiolabeled IgM was 10; the radioactivity level in the blood with F(ab)2 fragments was lower than with IgM, and so -camera imaging was workable with F(ab)2 fragments without background substraction. The tumor localization was studied over a period of 5 days by recording the distribution of the iodinated fragments in the tumor-bearing leg compared with that in the normal leg, and by computer analysis of the region of interest. F(ab)2 fragments gave better results than intact IgM in tumor visualization. Nevertheless, the rapid clearance of this antibody or its F(ab)2 fragments make them hardly suitable as carriers of toxic drugs.
Abbreviations used are: MEM Minimum essential medium; SDS sodium dodecylsulfate; PAGE polyacrylamide gel electrophoresis 相似文献
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8.
Elisabeth Steichen-Gersdorf Holly H. Gallion Deborah Ford Catherine Girodet Douglas F. Easton Richard A. DiCioccio Gareth Evans Margaret A. Ponder Carole Pye Sylvie Mazoyer Tetsuro Noguchi Fabienne Karengueven Hagay Sobol A. Hardouin Yves-Jean Bignon M. Steven Piver Simon A. Smith Bruce A. J. Ponder 《American journal of human genetics》1994,55(5):870-875
In a study of nine families with “site-specific” ovarian cancer (criterion: three or more cases of epithelial ovarian cancer and no cases of breast cancer diagnosed at age <50 years) we have obtained evidence of linkage to the breast-ovarian cancer susceptibility gene, BRCA1 on 17q12-21. If the risk of cancer in these families is assumed to be restricted to the ovary, the best estimate of the proportion of families linked to BRCA1 is .78 (95% confidence interval .32–1.0). If predisposition to both breast and ovarian cancer is assumed, the proportion linked is 1.0 (95% confidence interval .46–1.0). The linkage of familial site-specific ovarian cancer to BRCA1 indicates the possibility of predictive testing in such families; however, this is only appropriate in families where the evidence for linkage to BRCA1 is conclusive. 相似文献
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