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61.
E Sugiyama A Cantagrel T Reno F Stafford-Brady E T Yeh J V Bonventre 《Cellular immunology》1990,130(2):271-280
Ly-6A is a glycosyl-phosphatidylinositol (GPI)-anchored molecule that participates in murine T cell activation. Activation of T cell hybridomas with anti-Ly-6A monoclonal antibody (mAb) leads to production of interleukin-2 (IL-2), but also to a paradoxical growth inhibition, which was used to select for signaling mutants. Fifteen subclones derived from two independent mutageneses and anti-Ly-6A selection were characterized. Thirteen subclones responded poorly or not at all to soluble anti-Ly-6A mAb. Although the selective pressure was exerted through Ly-6A, only one mutant did not express the Ly-6A antigen. Interestingly, 10 of the 15 subclones expressed either nondetectable or a very low level of T cell receptor/CD3 complex (TCR/CD3). Preferential expansion of TCR/CD3 expression mutants following anti-Ly-6A selection further established functional linkage between Ly-6A and TCR/CD3 complex. The mechanism of the functional coupling was investigated by analyzing the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2), one of the early events in T cell activation. We showed that PIP2 was not hydrolyzed in response to anti-Ly-6A in TCR/CD3-negative mutants. Aluminum fluoride, which activates G protein directly, did induce PIP2 hydrolysis in these cells. These data suggest that activation signals originated from Ly-6A must be transmitted first to TCR/CD3 complex, which then couples to the G protein/phospholipase C system. A similar requirement also applies to the Thy-1 protein and lectin receptors. Thus, the TCR/CD3 complex plays a central role in the integration and transmission of activation signals that originated from several T cell surface molecules. 相似文献
62.
Transfer of 1-pyrroline-5-carboxylate as oxidizing potential from hepatocytes to erythrocytes. 总被引:2,自引:0,他引:2 下载免费PDF全文
The interconversions of proline and 1-pyrroline-5-carboxylate form an intercellular cycle that is the basis of a metabolic interaction between hepatocytes and erythrocytes. The cycle transfers oxidizing potential from hepatocytes to erythrocytes, which stimulates pentose phosphate pathway in erythrocytes. This interaction depends on the differential metabolism of proline and 1-pyrroline-5-carboxylate in erythrocytes and hepatocytes and consists of the following: in hepatocytes proline oxidase converts proline into 1-pyrroline-5-carboxylate, which is released into the medium and taken up by erythrocytes; erythrocyte 1-pyrroline-5-carboxylate reductase converts 1-pyrroline-5-carboxylate into proline and concomitantly generates NADP+; the generated oxidizing potential drives glucose metabolism through the pentose phosphate pathway in erythrocytes; finally, erythrocytes release proline into the medium, enabling it to re-enter hepatocytes and repeat the cycle. The increased activity of the pentose phosphate pathway in erythrocytes may enhance the production of 5-phosphoribosyl pyrophosphate, a necessary moiety for the processing of purines. 相似文献
63.
James M. Phang Sylvia J. Downing Grace Chao Yeh 《Biochemical and biophysical research communications》1980,93(2):462-470
The reactions catalyzed by proline oxidase and pyrroline-5-carboxylate reductase form a catalytic cycle linking the hexose-monophosphate pentose (HMP) pathway to mitochondrial ATP generation. The cycling of proline and pyrroline-5-carboxylate couples glucose oxidation to ATP generation by a mechanism independent of the Embden-Meyerhof pathway and the tricarboxylic acid cycle. 相似文献
64.
Dynamic light scattering studies have been conducted on the delipidated and detergent-removed (Ca2+ + Mg2+)-ATPase protein assemblies. Specific characterization of the state of aggregation and the extent of conformation change upon delipidation and detergent removal has been made. The results show that the prominent species are dimers and tetramers of very globular nature, with axial ratios of less than 2 : 1. The hydrodynamic radii of the dimers and the tetramers are, respectively, 57.5 Å and 74.5 Å.The globular nature of these observed entities differ from the delipidated ATPase proteins recently obtained (LeMaire, M., Jorgensen, K.E., Roigaard-Petersen, H. and Moller, J.V. (1976) Biochemistry 15, 5805–5812). Present results suggest that upon the removal of detergents from the lipid-free ATPase protein assembly, only a rather limited degree of aggregation takes place. Such a condition is consistent with models of the membrane protein system which has limited regions of hydrophobic contact. Oligomeric assemblies with aqueous channels is a possible active Ca2+ transport model consistent with results of the present data, as well as the data from several other recent studies. 相似文献
65.
66.
Interactions of aminopyridines with potassium channels of squid axon membranes. 总被引:26,自引:0,他引:26 下载免费PDF全文
The effects of aminopyridines on ionic conductances of the squid giant axon membrane were examined using voltage clamp and internal perfusion techniques. 4-Aminopyridine (4-AP) reduced potassium currents, but had no effect upon transient sodium currents. The block of potassium channels by 4-AP was substantially less with (a) strong depolarization to positive membrane potentials, (b) increasing the duration of a given depolarizing step, and (c) increasing the frequency of step depolarizations. Experiments with high external potassium concentrations revealed that the effect of 4-AP was independent of the direction of potassium ion movement. Both 3- and 2-aminopyridine were indistinguishable from 4-AP except in potency. It is concluded that aminopyrimidines may be used as tools to block the potassium conductance in excitable membranes, but only within certain specific voltage and frequency limits. 相似文献
67.
L J Yeh C Y Yang R P Beasley J L Gale S P Wang J T Grayston 《Chinese journal of microbiology》1975,8(2):120-132
This study was undertaken to clarify the natural history and pathogenesis of trachoma. A group of families who live in a formerly trachoma hyperendemic area of Southern Taiwan were placed under continuous surveillance. The development in recent years of the micro immunofluorescence test for trachoma antibody, along with improved cell culture isolation methods, have allowed this surveillance to include repeated effective laboratory studies in addition to clinical observations. After four years' study of one group of families and three years of another, a number of interesting findings have been obtained. Evidence is presented supporting our hypothesis that trachoma is a disease of immumopathology and results from repeated reinfections with the trachoma organisms. The clinical findings of papillae, especially those of an acute nature, has been the clinical finding most closely associated with the isolation of the organism and the demonstration of antibody. Evidence is presented that transmission of the organism is usually within the family group. Although only trachoma immunotypes B and C previously had been associated with trachoma infection on Taiwan, data is presented from one family in which type D infections occurred. While a series of new and reinfections with trachoma organisms were demonstrated in some of the families under observation, the majority of the families not only showed no new infections but showed spontaneous healing or disappearance of clinical and laboratory evidence of trachoma infection. This tendency of active trachoma infection to disappear from a family in the absence of transmission of the organism parallels the rapid fall and prevalence of active trachoma on Taiwan during the past decade. 相似文献
68.
To reveal the presence of rhodopsin on the surface of the mouse retina, a scanning electron microscope study of the immunolabeling of rhodopsin was attempted. The glutaraldehyde-fixed mouse retina was treated first with rabbit antibodies specific against bovine rhodopsin and then with hemocynin-labeled goat antibodies specific against rabbit antibody. The distribution of hemocyanin label on mouse retina and the technique used for labeling are discussed. 相似文献
69.
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