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排序方式: 共有391条查询结果,搜索用时 31 毫秒
1.
Basic characteristics of human lung mast cell desensitization 总被引:1,自引:0,他引:1
Human lung parenchymal mast cells displayed both specific and nonspecific desensitization. The kinetics of both release and desensitization were approximately equal to 3 times faster than human basophils, but a similar relationship between release and desensitization suggests similar biochemistries in basophils and mast cells. Arachidonic acid metabolite (PGD2 and LTC4) release was slower to desensitize (t1/2 of 8 min) than histamine release (t1/2 of 3 min), the ratio of which is similar to the ratio observed in basophils. Ionophore A23187-induced release was unaffected by desensitization to anti-IgE antibody, and calcium-45 uptake was inhibited by desensitization, suggesting that desensitization inhibits the early post-cross-linking "influx" of calcium that is necessary for mediator release in mast cells. In contrast to the above similarities in basophil and mast cell desensitization, mast cell desensitization, unlike that of basophils was not inhibited by diisopropylfluorophosphate. 相似文献
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K M Leiferman G J Gleich G M Kephart H S Haugen K Hisamatsu D Proud L M Lichtenstein S J Ackerman 《Journal of immunology (Baltimore, Md. : 1950)》1986,136(3):852-855
Human eosinophils contain several distinctive proteins including eosinophil granule MBP and the membrane-associated CLC protein (lysophospholipase). Human basophils also contain these proteins, indicating biochemical similarities between eosinophils and basophils. To determine whether MBP or CLC protein is present in connective tissue mast cells, we studied human lung and cutaneous mast cells by immunofluorescence by utilizing specific antibodies to CLC and MBP. Cytocentrifuge slides of enriched lung mast cells and mast cells in sections of formalin-fixed, paraffin-embedded cutaneous tissue from urticaria pigmentosa lesions were stained for CLC and MBP. Neither pulmonary nor cutaneous mast cells stained for CLC protein or MBP. In contrast, lung and cutaneous eosinophils in the same preparations showed bright staining for both proteins. The failure to find CLC protein and MBP in mast cells provides additional evidence of dissimilarity between mast cells and basophils, and an immunochemical means to distinguish between them. 相似文献
4.
Cybulsky I. J.; Abel J. G.; Menon A. S.; Salerno T. A.; Lichtenstein S. V.; Slutsky A. S. 《Journal of applied physiology》1987,63(2):564-570
The contribution of cardiogenic oscillations to gas exchange during constant-flow ventilation was examined in 11 dogs. With the use of two variations of cardiopulmonary bypass to maintain the systemic and pulmonary circulation, the influence of cardiogenic oscillations was removed by arresting the heart. Cardiac arrest by ventricular fibrillation was associated with a mean decrease in alveolar ventilation of 43% in five dogs on right and left heart bypass. However, successful defibrillation and return of the prearrest level of alveolar ventilation could not be achieved; thus we studied six dogs on left heart bypass. Alveolar ventilation decreased an average of 37% with cardiac arrest, and defibrillation resulted in a return of alveolar ventilation to 81% of the prearrest value. These results are consistent with previous predictions that cardiogenic oscillations are an important mechanism of gas transport during constant-flow ventilation. 相似文献
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Carrier-mediated transport of the folic acid analogue, methotrexate, in the L1210 leukemia cell 总被引:20,自引:0,他引:20
I D Goldman N S Lichtenstein V T Oliverio 《The Journal of biological chemistry》1968,243(19):5007-5017
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Comparison of deuterated leucine, valine, and lysine in the measurement of human apolipoprotein A-I and B-100 kinetics 总被引:3,自引:0,他引:3
A H Lichtenstein J S Cohn D L Hachey J S Millar J M Ordovas E J Schaefer 《Journal of lipid research》1990,31(9):1693-1701
The production rates of apolipoprotein (apo)B-100 in very low density lipoprotein and in low density lipoprotein and apolipoprotein A-I in high density lipoprotein were determined using a primed-constant infusion of [5,5,5,-2H3]leucine, [4,4,4,-2H3]valine, and [6,6-2H2,1,2-13C2]lysine. The three stable isotope-labeled amino acids were administered simultaneously to determine whether absolute production rates calculated using a stochastic model were independent of the tracer species utilized. Three normolipidemic adult males were studied in the constantly fed state over a 15-h period. The absolute production rates of very low density lipoprotein apoB-100 were 11.4 +/- 5.8 (leucine), 11.2 +/- 6.8 (valine), and 11.1 +/- 5.4 (lysine) mg per kg per day (mean +/- SDM). The absolute production rates for low density lipoprotein apoB-100 were 8.0 +/- 4.7 (leucine), 7.5 +/- 3.8 (valine), and 7.5 +/- 4.2 (lysine) mg per kg per day. The absolute production rates for high density lipoprotein apoA-I were 9.7 +/- 0.2 (leucine), 9.4 +/- 1.7 (valine, and 9.1 +/- 1.3 (lysine) mg per kg per day. There were no statistically significant differences in absolute synthetic rates of the three apolipoproteins when the plateau isotopic enrichment values of very low density lipoprotein apoB-100 were used to define the isotopic enrichment of the intracellular precursor pool. Our data indicate that deuterated leucine, valine, or lysine provided similar results when used for the determination of apoA-I and apoB-100 absolute production rates within plasma lipoproteins as part of a primed-constant infusion protocol. 相似文献
8.
11 beta-hydroxysteroid dehydrogenase (11-HSD, EC 1.1.1.146) from rat renal cortex microsomes was solubilized using several detergents, the most effective being Zwittergent 3-10 and Triton X-100. The activity ratio oxidation/reduction of the reversible reaction corticosterone in equilibrium 11-dehydrocoticosterone varied depending on the detergent used. We attribute this variation to direct effects of different detergents on enzyme kinetics. In contrast, comparable results obtained with liver 11-HSD have been attributed to the possibility of spatially separated 11-oxidase and 11-reductase activities. In order to test whether renal 11-HSD represents a uniform oxido-reductase as generally assumed, or a dual enzyme system as has been recently proposed an attempt was made to characterize 11-HSD solubilized from renal microsomal fractions using isoelectric focusing (IEF). When 11-HSD was extracted with 1% Triton X-100 (= partially solubilized fraction) a heterogenous peak pattern was obtained. In contrast, IEF of 11-HSD extracted with 10% Triton X-100 (= delipidated fraction) resulted in a single peak at about pH 5.9 with both oxidative and reductive activity at practically identical positions within the gels. From this observation we conclude that the degree of detergent solubilization of a membrane bound protein affects its amphoteric properties and that removal of membranous lipids is a prerequisite for the analysis of its behaviour. Since the more delipidated fraction of 11-HSD revealed only one activity peak the data are compatible with the uniform enzyme concept since oxidative and reductive activities of renal cortical 11-HSD could not be separated. 相似文献
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Nielsen J; Peixoto AA; Piccin A; Costa R; Kyriacou CP; Chalmers D 《Molecular biology and evolution》1994,11(6):839-853
The region of the clock gene period (per) that encodes a repetitive tract
of threonine-glycine (Thr-Gly) pairs has been compared between Dipteran
species both within and outside the Drosophilidae. All the non-
Drosophilidae sequences in this region are short and present a remarkably
stable picture compared to the Drosophilidae, in which the region is much
larger and extremely variable, both in size and composition. The
accelerated evolution in the repetitive region of the Drosophilidae appears
to be mainly due to an expansion of two ancestral repeats, one encoding a
Thr-Gly dipeptide and the other a pentapeptide rich in serine, glycine, and
asparagine or threonine. In some drosophilids the expansion involves a
duplication of the pentapeptide sequence, but in Drosophila pseudoobscura
both the dipeptide and the pentapeptide repeats are present in larger
numbers. In the nondrosophilids, however, the pentapeptide sequence is
represented by one copy and the dipeptide by two copies. These observations
fulfill some of the predictions of recent theoretical models that have
simulated the evolution of repetitive sequences.
相似文献