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21.
Proteose peptone-induced peritoneal macrophages from CBA/J (H-2k) mice have been fused to a hypoxanthine phosphoribosyltransferase-negative variant of the P388D1 (H-2d) murine macrophage cell line. Six hybrid clones were isolated following HAT selection and further characterized. Five of the six clones express class I antigens of both parental haplotypes by microelisa and by flow cytometric analysis. Class II antigen expression of both haplotypes was apparent following a 72-hr incubation of the hybrids with concanavalin A-stimulated rat spleen cell supernatant. However, I-Ad was expressed in all hybrids to a greater extent than I-Ak. Three clones with the highest level of I-Ak expression, E5, C2, and C4, were capable of antigen presentation to the I-Ak-restricted T-cell line, D10.G4.1. LPS induction of the hybrids resulted in a 2- to 15-fold increase in the amount of IL-1 produced relative to the P388D1 parent. Finally, in distinction to P388D1, all hybrids demonstrated increased Fc-mediated erythrophagocytosis of chromium-labeled antibody-coated erythrocytes. These murine macrophage hybrids appear stable and should serve as useful models in understanding the regulation of macrophage function. 相似文献
22.
The relative cytotoxicity and mutagenicity of cyclobutane pyrimidine dimers and (6-4) photoproducts in Escherichia coli cells 总被引:4,自引:0,他引:4
In order to calculate the relative cytotoxicity and mutagenicity of (5-6) cyclobutane pyrimidine dimers and (6-4) photoproducts, we have measured survival and mutation induction in UV-irradiated excision-deficient E. coli uvrA cells, with or without complete photoreactivation of the (5-6) dimers. Radioimmunoassays with specificity for (5-6) dimers or (6-4) photoproducts have shown that maximum photoreactivation eliminates all of the (5-6) dimers produced up to 10 Jm-2 254-nm light, while it has no effect on (6-4) photoproducts. These results were confirmed by measuring the frequency of T4 endonuclease V-sensitive sites. Based on the best fit equations for survival and mutation induction, we have found that the calculated cytotoxicity of (6-4) photoproducts is similar to that of (5-6) dimers; however, the former is much more mutagenic than the latter. 相似文献
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25.
B淋巴细胞在多向造血祖细胞生长中的地位 总被引:3,自引:0,他引:3
小鼠骨髓细胞在体外培养中,加入用流式自由电泳法分离所得的高纯度正常B淋巴细胞,可使多向祖细胞(CFU-mix)集落增加至5倍;加入小鼠B淋巴瘤细胞株的条件培基(M_(12.4.1)-CM)时,CFU-mix数也可增加至4倍。单集落形态学分析结果表明M_(12.4.1)-CM可加强CFU-GEMm及p-BFU-E等早期造血祖细胞的增殖与分化。小鼠高纯度B细胞样品在体外培养中加入1000 rad照射的骨髓细胞可出现CFU-mix集落,如果再加入适量的小鼠肺条件培基,则CFU-mix数量比对照大15倍,其集落性质为CFU-GEMm,GMm及p-BFU-E。在此培养中加不同稀释度抗小鼠IgM血清,结果CFU-mix的产率与抗IgM血清的浓度成直线反比关系,当加入1:10抗小鼠IgM血清时,CFU-mix为0。作者假设在一定培养条件下,IgM阳性的部分B细胞可返祖转化为CFU-mix。 相似文献
26.
Proteoglycans from bovine nasal and articular cartilages. Fractionation of the link proteins by wheat germ agglutinin affinity chromatography 总被引:2,自引:0,他引:2
H U Choi L H Tang T L Johnson L Rosenberg 《The Journal of biological chemistry》1985,260(24):13370-13376
Two forms of link protein, 46 and 51 kDa, are present in proteoglycan aggregates from both bovine nasal and bovine articular cartilages. Studies reported here show that the link proteins bind to concanavalin A, Lens culinaris agglutinin, Ricinus communis agglutinin, soybean agglutinin, and wheat germ agglutinin lectins. When the link proteins are eluted from these lectins with appropriate competing sugars, the 46- and the 51-kDa link proteins elute together and no separation is achieved. However, when the link proteins bound to wheat germ agglutinin are eluted with a 0 to 4 M guanidine hydrochloride linear gradient, a good separation of the 46- and 51-kDa link proteins is achieved. Wheat germ agglutinin affinity chromatography has been used on a preparative scale to isolate the 51-kDa link protein from mature bovine articular cartilage to homogeneity, in amounts sufficient to examine its effect on proteoglycan aggregate size and stability in sedimentation velocity studies. Proteoglycan aggregates were reassembled from proteoglycan monomers and hyaluronate in the absence of link protein, in the presence of both 46- and 51-kDa link proteins, and in the presence of the individual 51-kDa link protein. The sizes of the aggregates were compared in terms of sedimentation coefficients (s(0)20). The stability of the aggregates was compared in terms of the per cent aggregate present at pH 7 and 5. At pH 7, the sedimentation coefficients (s(0)20) of link-free aggregates, aggregates formed with both link proteins, and aggregates formed with 51-kDa link protein were 72, 93, and 112 S, respectively. Thus, the 51-kDa link protein has a pronounced effect on aggregate size. The link-free aggregate was grossly unstable, and only 36% aggregate was present at pH 5. The aggregate formed with both link proteins was effectively stabilized against dissociation and 79% aggregate was present at pH 5. The aggregate formed with 51-kDa link protein was not effectively stabilized against dissociation, and only 60% aggregate was present at pH 5. Thus, despite its pronounced effect on aggregate size, the 51-kDa link protein does not effectively stabilize the proteoglycan aggregate against dissociation. These results suggest that the 51-kDa link protein may selectively increase aggregate size, while the 46-kDa link protein may be required to effectively stabilize the proteoglycan aggregate against dissociation. 相似文献
27.
Characterization of temperature-sensitive [3H]serotonin (5-HT) binding sites (1 and 4 nM Kd sites) revealed complex inhibition by neuroleptics and serotonin antagonists. There was no simple correlation with affinities for S1 and S2 receptors. pretreatment (48 h before) with mianserin did not alter Bmax or Kd for the 1 nM Kd [3H]5-HT site, although [3H]ketanserin (S2) densities were decreased by 50%. This suggested that possible S2 components of [3H]5-HT binding must be negligeable, even though ketanserin competed with high affinity (IC50 = 3 nM) for a portion of the 1 nM Kd [3H]5-HT site. Low concentrations of mianserin inhibited the 1 nM Kd [3H]5-HT site in a non-competitive manner, as shown by a decrease in Bmax with no change in Kd after incubation. The complex inhibition data may therefore represent indirect interactions through another site. 相似文献
28.
Joanna Strosznajder Laurie Foudin Wilson Tang Grace Y. Sun 《Journal of neurochemistry》1983,40(1):84-90
Arachidonate incorporation into synaptosomal phospholipids was shown to be affected by factors including the procedure for preparation of the membrane fractions and preincubation of synaptosomes prior to assay of incorporation of arachidonate into both phosphatidylcholine (PC) and phosphatidylinositol (PI). However, the inhibition toward incorporation into PIs, but not PCs, was fully reversed when the membranes were washed with bovine serum albumin. A twofold increase in arachidonate incorporation into PIs was also observed when freshly prepared synaptosomes were washed with serum albumin immediately before assay of incorporation activity. The inhibitory action is thought to be due to an increase in polyunsaturated fatty acids and/or their oxidation products which may then elicit a special effect on the acyltransferase responsible for transferring arachidonate into phosphatidylinositols. The differences in fatty acid uptake and response to serum albumin also suggest the presence of different acyltransferase for acyl transfer to PIs and PCs. 相似文献
29.
S P Tang T G Spiro K Mukai T Kimura 《Biochemical and biophysical research communications》1973,53(3):869-874
Raman spectra have been recorded for native and selenium substituted adrenodoxin in dilute solution. Adrenodoxin shows three bands at 397, 350 and 297 cm?1, all polarized, which can be associated with the iron-sulfur core. Selenium substitution leaves the 350 cm?1 band essentially unshifted, but the other two bands disappear and are replaced by new bands at 355 and 263 cm?1. The 350 cm?1 band is assigned to stretching of iron-sulfur (cysteine) bonds, while the 397 and 297 cm?1 bands are associated with vibrations of the labile sulfur atoms. The iron-selenium charge transfer bands were observed at 438 and 480 nm for the oxidized form and at 580 nm for the reduced form. The reduced selena-adrenodoxin displayed absorption maxima at 4, 450 and 5, 550 cm?1, which can be assigned to the d-d transitions of high-spin ferrous ion. From this data and the reported g-values of electron paramagnetic resonance signals, the spin-orbit coupling constants were calculated to be 170 and 210 cm?1 for the respective d-d transitions. 相似文献
30.
On the specificity of human gastricsin and pepsin 总被引:2,自引:0,他引:2