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91.
Antibodies to peptide determinants in transforming growth factor beta and their applications 总被引:13,自引:0,他引:13
Polyclonal antibodies have been raised to a series of synthetic peptides which correspond to essentially all regions of the transforming growth factor beta 1 (TGF-beta 1) molecule. All antisera were evaluated for their abilities to react with TGF-beta 1 and TGF-beta 2 in either the native or reduced form in enzyme-linked immunosorbent assays, Western blots, and immunoprecipitation assays. While all antisera demonstrated some ability to recognize TGF-beta 1 in these systems, there was limited cross-reactivity with TGF-beta 2, suggesting that substantial sequence or conformational differences exist between the two growth factors. On Western blots 5-10 ng of purified human platelet TGF-beta 1 could be detected when probed with affinity-purified peptide antisera generated against peptides corresponding to residues 48-77, 50-75, and 78-109 of the 112 amino acid TGF-beta 1 monomer. Antisera raised against peptides 50-75 and 78-109 were most effective in immunoprecipitating reduced and native 125I-TGF-beta 1, respectively. The antisera also were tested for their effectiveness in blocking the binding of 125I-TGF-beta 1 to its receptor. Anti-peptide 78-109 and anti-peptide 50-75 blocked 80% and 40% of the binding, respectively, while antibodies against amino-terminal peptides were without effect. These data suggest that the carboxyl-terminal region of TGF-beta 1 may play a significant role in the binding of the native ligand to its receptor. 相似文献
92.
Multidrug resistance is mediated by P-glycoprotein, an integral plasma membrane component which is thought to function as a drug export pump. This model can explain drug resistance, but fails to account for the broader pleiotropy of the multidrug resistance phenotype. We report here a freeze-fracture study revealing increases in the densities of protoplasmic face intramembrane particles in multidrug-resistant Chinese hamster ovary (CHO) and human leukemic cells. The intramembrane particle density in a CHO cell revertant which had lost the characteristics of the multidrug resistance phenotype was indistinguishable from that of the drug-sensitive parental cell line. This demonstration of a global multidrug resistance-linked change in plasma membrane architecture may have significant implications for understanding the variety of concurrent membrane-related changes which are not easily explained by the current model for multidrug resistance. 相似文献
93.
A surface component on GH3 pituitary cells that recognizes transforming growth factor-beta, activin, and inhibin 总被引:4,自引:0,他引:4
S Cheifetz N Ling R Guillemin J Massagué 《The Journal of biological chemistry》1988,263(33):17225-17228
We have examined the ability of various forms of activin and inhibin, which are structurally related to transforming growth factor-beta (TGF-beta), to interact with various types of cell surface TGF-beta binding sites. Activin AB, inhibin A, and inhibin B were unable to compete with 125I-TGF-beta 1 for binding to the TGF-beta receptor types I, II, or III that coexist in human skin fibroblasts, rat liver epithelial cells, and mink lung epithelial cells. In contrast, activins and inhibins effectively competed for TGF-beta 1 binding to GH3 rat pituitary tumor cells. Binding of TGF-beta 1 to GH3 cells was mediated by about 2700 sites/cell with a Kd = 90 pM. Affinity labeling of these GH3 binding sites by cross-linking to 125I-TGF-beta 1 yielded 70-74-kDa labeled complexes distinct from previously identified TGF-beta binding components. Labeling of these 70-74-kDa components with 125I-TGF-beta 1 was inhibited by TGF-beta 1, TGF-beta 2, activin AB, and inhibin B at concentrations in the high picomolar to low nanomolar range, but it was not significantly affected by other polypeptide hormones and growth factors tested. The 70-74-kDa labeled GH3 components represent a novel type of cell surface TGF-beta binding protein that is unique in its ability to recognize various other members of the TGF-beta family of bioactive polypeptides. 相似文献
94.
Effects of ethinyl estradiol on intestinal membrane structure and function in the rabbit 总被引:1,自引:0,他引:1
S M Schwarz J B Watkins S C Ling J C Fayer M Mone 《Biochimica et biophysica acta》1986,860(2):411-419
Structural and functional properties of the small intestinal microvillus membrane were evaluated in the rabbit after administration of ethinyl estradiol, a synthetic estrogen with a demonstrated propensity to alter hepatic membrane lipid fluidity, and promote cholestasis. In the jejunum, no estrogen-induced changes in microvillus membrane total lipid, cholesterol or phospholipid content were observed. However, the ileal microvillus membrane in estradiol-treated animals demonstrates significant reductions vs. controls (per mg protein) in total lipid (0.55 milligrams vs. 0.89 milligrams) [corrected] and phospholipid (206.7 micrograms vs. 304.91 micrograms) (p less than 0.001) content, as well as modifications in specific phospholipid species. The increase in the ileal microvillus membrane cholesterol: phospholipid molar ratio (0.65 vs. 0.51, p less than 0.05) was associated with a significant decrease in membrane lipid fluidity reflected by an increase in fluorescence anisotropy measurements utilizing diphenyl hexatriene as the fluorophore (r at 25 degrees C = 0.306 vs. 0.282, p less than 0.05). Thermotropic lipid phase transitions, assessed by Arrhenius plots of both fluorescence data and ileal microvillus membrane p-nitrophenylphosphatase activity demonstrate that phase changes occur between and 24 and 28 degrees C in both treated and untreated groups. Within the temperature range studied (40-10 degrees C) no differences from control were observed in microvillus membrane alkaline phosphatase activity following estrogen treatment. These data therefore indicate that ethinyl estradiol-induced effects on microvillus membrane lipid composition and physical properties occur predominantly in the ileum and appear to be related, in part, to specific alterations in the availability of phospholipid following estrogen treatment. 相似文献
95.
Labelling of amoeboid microglial cells in rats of various ages following an intravenous injection of horseradish peroxidase 总被引:2,自引:0,他引:2
The macrophagic amoeboid microglial cells in the corpus callosum of postnatal rats were labelled following an intravenous injection of horseradish peroxidase (HRP). The earliest time when these cells were labelled was 3 h after the injection of HRP in postnatal (1-10 days) rats. Similar cells around the mesencephalic aqueduct and the fourth ventricle were also labelled. These cells, however, were weakly labelled in developing (11-20 days) and unlabelled in weaning (21-30 days) rats. The results suggest that in the postnatal rats, the HRP passed through the endothelial lining of the blood vessels and was then ingested by the amoeboid microglial cells. In the developing and older rats, the wall of blood vessels had developed fully thereby preventing the free passage of HRP into the brain tissues. 相似文献
96.
97.
在多年采集分离酵母菌的基础上,本文报道其中43属的600多株主要与担子菌有关的酵母及其他酵母的DBB反应,其中某些菌以往尚未测定过,从而广泛比较了担子菌酵母、子囊菌酵母与某些类酵母的区别。此外在方法上,摸索了其他未见报道的重氮盐的显色效果,发现固红B盐对布掷孢酵母(Bulleta Derx)的反应比DBB更灵敏。同时试验了热碱·乙醇处理细胞的快速DBB测试法,用此法测定某些疑难菌株,结果稳定,可大大缩短测试周期,并适用于多毛有气生菌丝的菌类。 相似文献
98.
99.
本工作研究了大鼠延髓中缝核在心血管活动调整中的作用。通过埋植套管向大鼠延髓中缝核区注射神经元兴奋剂谷氨酸钠5-μg可明显降低血压,抑制交感神经传出活动,心率无显著改变。降血压效应可被脊髓蛛网膜下腔注射5-HT受体阻断剂肉桂硫胺50μg,或腹腔注射赛庚啶15mg/kg所部分对抗;并可被皮下注射阿片受体阻断剂纳洛酮1mc/kg所削弱。结果提示:延髓中缝核-脊髓5-HT下行通路对脊髓的血管调节功能起抑制性影响,内源性阿片样物质可能参与该机制。 相似文献
100.
Antagonistic effect of interferon-beta on the interferon-gamma-induced expression of Ia antigen in murine macrophages 总被引:5,自引:0,他引:5
The cell surface expression of I region-associated (Ia) antigens by murine and human macrophages has been shown by investigators from a number of laboratories to be induced in a dose-dependent fashion by IFN-gamma, which is free of other lymphokines. The experiments described in this report demonstrate that fibroblast-derived IFN-beta exerts an antagonistic effect on IFN-gamma induced Ia expression in murine macrophages. Simultaneous addition of IFN-beta and IFN-gamma to peritoneal exudate macrophages results in decreased Ia expression when compared with macrophages treated with IFN-gamma only. Different sources of highly purified IFN-beta, as well as a recombinant human IFN-alpha (A/D Bgl; shown previously to be as active as IFN-beta in several other murine systems) acted in a similar antagonistic fashion to IFN-gamma-induced Ia induction. The down-regulation of Ia expression by IFN-beta is dose-dependent over a concentration range up to 100 U/ml. Time-course experiments indicated that for IFN-beta to down-regulate IFN-gamma-induced Ia, it had to be present either before stimulation with IFN-gamma or during the first 24 hr of simultaneous stimulation. Further experiments in which a highly specific antibody against IFN-alpha/beta was added to the cultures confirmed the findings of the time-course experiments. Inhibitors of the arachidonic acid pathway failed to reverse the effect of IFN-beta to reduce Ia antigen expression, which suggests that this inhibition is not prostaglandin mediated. Thus, these findings support a role for type I IFN as naturally occurring substances that negatively regulate the expression of class II molecules. 相似文献