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排序方式: 共有407条查询结果,搜索用时 15 毫秒
1.
C Mapp J Hartiala O L Frick R L Shields W M Gold 《Journal of applied physiology》1986,61(4):1467-1474
The relationship between airway responsiveness to inhaled antigen and histamine, immunologic release of lung histamine, immunologic responsiveness of skin, and specific immunoglobulin E (IgE) antibodies were examined in 11 inbred allergic dogs immunized with extracts of ragweed and grass and 5 nonimmunized control dogs from the same colony. Airway responsiveness to antigen and histamine was characterized by the doses that increased the airflow resistance of the total respiratory system to twice the control values (ED200). Highly significant correlations were found between airway responsiveness and cutaneous responsiveness to antigen and other immunologic characteristics (e.g., IgE and histamine released from lung by inhaled antigen) in all dogs. In ragweed-sensitized dogs, there was an inverse correlation between immunologic responsiveness (reflected by the cutaneous response to antigen and histamine released from lung by inhaled antigen) and nonimmunologic responsiveness of airways (histamine ED200: r = 0.73, P less than 0.05 and r = 0.75, P less than 0.01, respectively). Antigen ED200 was also correlated with histamine release from lung after antigen inhalation (r = 0.74; P less than 0.01). We conclude that airway reactions to inhaled antigen in allergic dogs are dependent not only on immunologic factors but also on the degree of nonimmunologic airway responsiveness to histamine and that these factors are correlated inversely. 相似文献
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Duodenal goblet cells and Brunner's-gland cells obtained from two species of New World monkeys (Saimiri sciureus and Saguinus fuscicollis) were studied using conventional histochemical methods and by applying a panel of 17 labelled lectins. The secretions of both goblet and Brunner's-gland cells were found to contain neutral mucosubstances, while those of goblet cells also exhibit acid and sulphated carbohydrate components. Lectin binding studies allowed a more detailed analysis of the mucus glycoproteins. Marked differences between the two examined species were not detected. N-Acetyl-galactosamine, galactose, fucose and N-Acetyl-glucosamine were found to be the predominant sugar residues in Brunner's-glands glycoproteins, with mannose and glucose being only minor components. 相似文献
4.
Separation of multiple components of HeLa cell nuclear extracts required for pre-messenger RNA splicing 总被引:16,自引:0,他引:16
Components essential for nuclear pre-messenger RNA splicing have been partially purified from HeLa cell nuclear extracts by chromatography on DEAE-Sepharose, heparin-Sepharose, Mono Q, and Mono S. We have obtained six fractions which, when combined, efficiently splice a synthetic adenovirus 2 major late RNA substrate in vitro. All fractions contain components that support the formation of splicing intermediates (the cleaved 5' exon and the intron-exon 2 lariat). At least one of the fractions also contains an activity that is essential for the second step in the splicing reaction, namely cleavage at the 3' splice site and exon ligation. Two of the fractions are enriched in the major small nuclear ribonucleoprotein particles U1, U2, U4/U6, and U5. They participate in the formation of the splicing complexes which precedes the cleavage and ligation reactions. The remaining four fractions appear to contain protein factors, as suggested by their resistance to micrococcal nuclease. 相似文献
5.
Cytidine deaminase, purified to homogeneity from constitutive mutants of Escherichia coli, was found to bind the competitive inhibitors pyrimidin-2-one ribonucleoside (apparent Ki = 3.6 x 10(-7) M) and 5-fluoropyrimidin-2-one ribonucleoside (apparent Ki = 3.5 x 10(-8) M). Enzyme binding resulted in a change of the lambda max of pyrimidin-2-one ribonucleoside from 303 nm for the free species to 239 nm for the bound species. The value for the bound species was identical with that of an oxygen adduct formed by combination of hydroxide ion with 1,3-dimethyl-2-oxopyrimidinium (239 nm), but lower than that of a sulfur adduct formed by combination of the thiolate anion of N-acetylcysteamine with 1,3-dimethyl-2-oxopyrimidinium (259 nm). The results suggest that pyrimidin-2-one ribonucleoside is bound by cytidine deaminase as an oxygen adduct, probably the covalent hydrate 3,4-dihydrouridine, rather than intact or as an adduct involving a thiol group of the enzyme. In dilute solution at 25 degrees C, the equilibrium constant for formation of a single diastereomer of 3,4-dihydrouridine from pyrimidin-2-one ribonucleoside was estimated as approximately 4.7 x 10(-6), from equilibria of dissociation of water, protonation of 1-methylpyrimidin-2-one, and combination of the 1,3-dimethylpyrimidinium cation with the hydroxide ion.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
6.
Summary Duodenal goblet cells and Brunner's-gland cells obtained from two species of New World monkeys (Saimiri sciureus andSaguinus fuscicollis) were studied using conventional histochemical methods and by applying a panel of 17 labelled lectins. The secretions of both goblet and Brunner'-gland cells were found to contain neutral mucosubstances, while those of goblet cells also exhibit acid and sulphated carbohydrate components. Lectin binding studies allowed a more detailed analysis of the mucus glycoproteins. Marked differences between the two examined species were not detected.N-Acetyl-galactosamine, galactose, fucose andN-Acetyl-glucosamine were found to be the predominante sugar residues in Brunner's-glands glycoproteins, with mannose and glucose being only minor components.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday 相似文献
7.
C Y Cheng N A Musto G L Gunsalus J Frick C W Bardin 《The Journal of biological chemistry》1985,260(9):5631-5640
To determine how the androgen binding protein in human testes (hABP) is related to the serum protein, testosterone-estradiol binding globulin (hTeBG), both proteins were isolated and compared. The hABP in extracts of human testes was composed of two molecular species based on concanavalin A (ConA)-Sepharose chromatography. Form I hABP did not interact with ConA while Form II hABP bound to ConA and eluted with alpha-methylmannoside. Form I and Form II hABP from five batches of testes were then purified approximately 30,500- and 30,000-fold to apparent homogeneity by high-performance liquid chromatography and compared with hTeBG isolated from human pregnancy serum. Fractionation of both forms of hABP and hTeBG by polyacrylamide gel electrophoresis in the absence of sodium dodecyl sulfate suggested that the native forms of these proteins were indistinguishable. However, analysis of the purified proteins on sodium dodecyl sulfate-containing polyacrylamide gels indicated that all three were dimers and that each was composed of monomers of at least two sizes which were not present in equimolar concentrations. Two distinctive monomers or protomers of each protein were designated as heavy (H) and light (L) according to their electrophoretic mobilities on sodium dodecyl sulfate-polyacrylamide gels. The H and L protomers of Form I hABP showed apparent molecular weights of 55,000 and 52,000, respectively, in all preparations and were usually present in a 4:5 ratio (H:L). The two components of Form II hABP had apparent molecular weights of 53,000 and 48,000, respectively, and existed in a ratio of approximately 20:1. These two components could not be distinguished in some preparations where Form II hABP migrated as a broad band rather than as distinct protomers. By contrast, hTeBG, which was similar to Form II hABP with respect to ConA binding, always exhibited discrete H and L protomers in a 10:1 ratio. Photolysis of these highly purified proteins with delta 6-[3H]testosterone resulted in specific covalent labeling of their binding sites, confirming that the products identified by silver staining and immunoblotting were indeed steroid binding proteins. The H and L protomers of Form I hABP and hTeBG were separated and examined by peptide mapping using Staphylococcus aureus protease V8 and chymotrypsin. The comparison of the respective fragmentation patterns of protomers indicated that Form I hABP and hTeBG contained distinctive peptides.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
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蚕豆叶片发育与衰老过程中超氧物歧化酶活性与丙二醛含量变化 总被引:2,自引:0,他引:2
蚕豆植株叶片随茎节自上而下表现出明显的发育与衰老顺序,可作为衰老特征的是叶绿素和蛋白质含量明显下降。蚕豆叶中SOD活性主要定位于12 000× g离心后所得的上清液和叶绿体组分。衰老叶片的SOD总活性和叶绿体组分的相对活性都有所下降,SOD同工酶谱也发生了改变。O_2~ 产生速率随叶龄增大而稍上升;而MDA含量在叶片外观表现枯黄衰老征兆前就急剧上升。可能因为衰老叶片过氧化氢酶活性大幅度下降与SOD之间的不平衡,致使O_2~ 代谢中间产物累积而引起膜的损伤. 相似文献
10.
William r. Anderson Willi Frick G.Doyle Daves Douglas F. Barofsky Isomaro Yamaguchi Ding Chang Karl Folkers Sune Rosell 《Biochemical and biophysical research communications》1977,78(1):372-376
Mass spectra of underivatized hexa- and heptapeptide amides related to Substance P have been obtained with a conventional electron ionization mass spectrometer using sample vaporization from a tungsten wire by the technique of rapid heating, proton transfer ionization using ammonia, and photoplate recording of spectra. These spectra exhibit little evidence of sample pyrolysis and are readily interpreted to yield amino acid sequences. 相似文献