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H R Warner 《Journal of bacteriology》1983,154(3):1451-1454
The thermophile Thermus sp. strain X-1, grown at 70 degrees C, contains uracil-DNA glycosylase and apurinic endonuclease activities, both of which are known to have roles in the repair of DNA damaged by heat. Both of these activities have temperature optima of about 70 degrees C. However, neither of these activities is present in quantities significantly greater than that found in Escherichia coli grown at 37 degrees C. Therefore, it appears that thermophilic organisms may not contain greatly elevated levels of the enzymes thought to be involved in the repair of DNA damaged by heat. 相似文献
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Partial Purification and Characterization of Uracil-DNA Glycosylase Activity from Chloroplasts of Zea mays Seedlings 总被引:1,自引:1,他引:0 下载免费PDF全文
A uracil-DNA glycosylase activity has been purified about 750-fold from the chloroplasts of light-grown Zea mays seedlings. This report represents the first direct demonstration of a DNA-glycosylase repair activity in chloroplasts. The activity, in part, was associated with a chloroplast Triton X-100 sensitive membrane. Its apparent Km was 1.0 micromolar for a poly(dA-dT/U) substrate, and its molecular weight, as determined by gel filtration, was 18,000. The enzyme exhibited optimal activity at pH 7.0 with an atypically narrow pH tolerance. Activity was inhibited greater than 60% by 10 millimolar NaCl, 5 millimolar MgCl2, or 5 millimolar EDTA. Enzyme activity was inhibited 80% by 10 millimolar N-ethylmaleimide, a sulfhydryl group-blocking agent. The activity removed uracil more rapidly from single-stranded DNA than from double-stranded DNA. With this report, uracil-DNA glycosylase activity has now been attributed to all three DNA-containing organelles of eucaryotic cells. 相似文献
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Multiple myeloma: an immunologic profile. IV. The EA rosette-forming cell is a Leu-1 positive immunoregulatory B cell 总被引:3,自引:0,他引:3
M R MacKenzie T G Paglieroni N L Warner 《Journal of immunology (Baltimore, Md. : 1950)》1987,139(1):24-28
Patients with myeloma have a depressed capacity to respond to antigenic challenge. Studies in this laboratory have previously described an unclassified lymphoid cell which binds human erythrocytes coated with human immunoglobulin G (IgG) anti-D antibody (EA) as important in the inhibition of Ig synthesis in myeloma patients. Using monoclonal antibodies, two-color fluorescence studies, and flow cytometry, we characterized this EA cell as a Leu-1+ (cluster designation (CD) 5), Leu-12+ (CD 19), Leu-16+ (CD 20), B2+ (CD 21), Leu-14+ (CD 22), and HLA-DR+ B cell. The cell was negative for antibodies to Leu-2 (CD 8), Leu-3 (CD 4), Leu-4 (CD 3), Leu-5 (CD 2), Leu-7, Leu-8, Leu-11 (CD 16), Leu-M1 (CD 15), Leu-M3, and CALLA (CD 10). This profile is consistent with a Leu-1+ B cell and excludes a T cell, natural killer cell, and monocyte. Comparison of the relative role of these cells to the role of monocytes in the suppression of pokeweed mitogen-stimulated Ig synthesis was determined in serial studies on 19 myeloma patients. The mean (+/- SEM) percentage of inhibition of Ig synthesis by monocytes from stage I myeloma patients was 14 +/- 2.2%, from stage II patients was 37 +/- 3.5%, and from stage III patients was 51 +/- 4.7%. Inhibition of Ig synthesis by Leu-1+ EA cells was 46 +/- 1.5%, 48 +/- 1.6%, and 43 +/- 3.7% in stage I, II, and III patients, respectively. Immunosuppressive B cells are an important component of inhibition of Ig synthesis in the immunodeficiency of myeloma. 相似文献
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J A Warner K B Yancey D W MacGlashan 《Journal of immunology (Baltimore, Md. : 1950)》1987,139(1):161-165
We have found that basophils (n = 9) treated with pertussis toxin (1.0 microgram/ml) fail to respond to a subsequent challenge with either 1.0 microM f-Met peptide (p less than 0.0005) or 0.24 microgram/ml of C5a (p less than 0.0005) although their responses to anti-IgE (0.1 microgram/ml) and A23187 (1.0 microgram/ml) were unaltered. These results were confirmed in purified (average purity = 89 +/- 3%) basophils (n = 4). Leukotriene C4 release was also reduced to 15 +/- 5% of control (p less than 0.005) when pertussis toxin-treated basophils were exposed to 1.0 microM f-Met peptide, although no inhibition was noted when anti-IgE or A23187 were used as the stimuli. The effect of pertussis toxin on basophils appears to be independent of the presence of contaminating mononuclear cells. We found that pertussis toxin inhibited f-Met peptide-induced histamine release regardless of the magnitude of the stimulus (0.01 microM to 1.0 microM f-Met peptide), although anti-IgE-induced release was unaffected over a dose-response curve. The effect of pertussis toxin was found to be both time- and concentration-dependent. The maximum effects were obtained after a 3-hr incubation with 1 microgram/ml of toxin. Lower (0.01 to 0.05 microgram/ml) concentrations of toxin or shorter (30 to 60 min) incubation periods did not significantly (p greater than 0.05) inhibit mediator release. 相似文献
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Mapping of C2, Bf, and C4 genes to the swine major histocompatibility complex (swine leukocyte antigen) 总被引:1,自引:0,他引:1
W R Lie M F Rothschild C M Warner 《Journal of immunology (Baltimore, Md. : 1950)》1987,139(10):3388-3395
Three miniature swine lines, inbred for swine leukocyte antigen (SLA) haplotypes, a, c, and d, and a recombinant line, haplotype g, were analyzed for possible restriction fragment length polymorphisms (RFLP) by Southern blot hybridization with human C2, factor B (Bf), and C4 specific probes. The search for RFLP by using a human C2 probe failed to reveal any variants. However, a Taq I polymorphism was identified with the human Bf probe and Bam HI and Pvu II polymorphisms were identified with the human C4 probe. Overlapping restriction fragments were found with the C2 and Bf probes, which strongly suggests close linkage of C2 and Bf genes in swine. Segregation analyses of the Bf and C4 polymorphisms indicated that the polymorphic fragments followed a Mendelian pattern of inheritance. The recombinant haplotype g, which expresses class I genes of haplotype c and class II genes of haplotype d, was shown to produce an identical RFLP pattern, by using the Bf and C4 probes, as haplotype d, but different from that of haplotype c. This indicates that there is a close association of [C4-Bf-C2] and class II genes in miniature swine. Although these data do not show conclusively the location of the [C4-Bf-C2] genes, it is hypothesized that swine [C4-Bf-C2] genes are located between the class II and class I genes, as has been demonstrated in mouse and man. 相似文献