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21.
R W Dougherty P P Godfrey P C Hoyle J W Putney Jr R J Freer 《The Biochemical journal》1984,222(2):307-314
The relationship between receptor binding of the formylated peptide chemoattractant formylmethionylleucylphenylalanine (fMet-Leu-Phe), lysosomal enzyme secretion and metabolism of membrane phospholipids was evaluated in both human polymorphonuclear leucocytes (PMN) and the dimethyl sulphoxide (Me2SO)-stimulated human myelomonocytic HL-60 leukaemic cell line. In both cell types, exposure to fMet-Leu-Phe (100 nM) induced rapid lysosomal enzyme secretion (maximal release less than 30 s) and marked changes in the 32P-labelling of the inositol lipids phosphatidylinositol (PtdIns), phosphatidylinositol 4-phosphate (PtdIns4P), phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] as well as phosphatidic acid (PtdA). Specifically, levels of [32P]PtdIns and [32P]PtdIns(4,5)P2 decreased rapidly (peak decrease at 10-15s), with a subsequent increase at 30 s and later. PtdIns4P and PtdA showed only an increase. In Me2SO-differentiated HL-60 cells prelabelled with [3H]inositol for 20 h, fMet-Leu-Phe caused a net increase in the cellular content of [3H]inositol phosphates, including a rapid increase in [3H]inositol 1,4,5-trisphosphate, suggesting that PtdIns(4,5)P2 breakdown occurs by a phospholipase C mechanism. Both lysosomal enzyme secretion and changes in phospholipid metabolism occur over the same agonist concentration range with a similar time course. Binding of [3H]fMet-Leu-Phe, although occurring over the same concentration range, exhibited markedly slower kinetics. Although depletion of extracellular Ca2+ had no effect on ligand-induced polyphosphoinositide turnover, PtdIns turnover, PtdA labelling and lysosomal enzyme secretion were severely curtailed. These studies demonstrate a receptor-mediated enhancement of phospholipid turnover that correlates with a specific biological response to fMet-Leu-Phe. Further, the results are consistent with the idea that phospholipase C-mediated degradation of PtdIns(4,5)P2, which results in the formation of inositol trisphosphate, is an early step in the stimulus-secretion coupling pathway of the neutrophil. The lack of correlation between these two responses and the equilibrium-binding condition suggests that either these parameters are responsive to the rate of ligand-receptor interaction or only fractional occupation is required for a full biological response. 相似文献
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Immunoglobulin E decapeptide-induced 5-hydroxytryptamine release from rat peritoneal mast cells. Comparison with corticotropin-(1-24)-peptide, polyarginine, polylysine and antigen. 总被引:3,自引:0,他引:3
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A synthetic basic decapeptide from the C4 domain of human immunoglobulin E, corticotropin-(1-24)-peptide, polyarginine and polylysine stimulated up to 90% net release of 5-hydroxytryptamine from mast cells in rat peritoneal-cell suspensions. Concentration-response curves to all four polypeptides were parallel. Polyarginine and polylysine (EC50 congruent to 0.05 microM) were approximately 100-fold more potent than immunoglobulin E decapeptide and corticotropin-(1-24)-peptide (EC50 congruent to 5 microM). Polypeptide-induced release was complete within 5-10s. Immunoglobulin-E-decapeptide-induced 5-hydroxytryptamine release was additive to that induced by low concentrations of polyarginine, but non-additive to that induced by high concentrations of polyarginine. In contrast, release induced by antigen was additive along the whole length of the concentration-response curve to polyarginine. Benzalkonium chloride inhibited immunoglobulin-E-decapeptide- and polyarginine-induced 5-hydroxytryptamine release but enhanced release induced by immunological stimulation. 相似文献
25.
R E Godfrey 《Biophysical journal》1982,38(1):1-6
The transient dichroic ratio D = delta A parallel/delta A perpendicular has been measured in the visible absorption region of bacteriorhodopsin in purple membrane by a flash photolysis method. D is found to be wavelength independent throughout the visible absorption band, and reaches a maximum value of 2.75 +/- 0.15 on reduction of the excitation intensity. This value is close to that expected for a single nondegenerate transition dipole moment and is incompatible with the strong exciton coupling model used to explain circular dichroism (CD) spectrum of purple membrane. A time-dependent analysis of the exciton interaction and consideration of the coupling strength suggests an explanation of these observations. It is concluded that excitation interaction between retinals in purple membrane is of the weak or very weak type defined by Förster. 相似文献
26.
The time-resolved fluorescence emission anisotropy of 12-(9-anthroyloxy)stearic acid (12-AS) and 1,6-diphenyl-1,3,5-hexatriene (DPH) have been measured in dipalmitoylphosphatidylcholine liposomes in the presence and absence of 40 mol% cholesterol at temperatures above and below the phase transition temperature (41°C). By using a synchronously-pumped mode-locked frequency-doubled dye laser and single photon counting detection with an excitation response function of 300 picosecond, rotational correlation times down to less than 1 nanosecond could be resolved. Whereas DPH showed only small changes in the limiting anisotropy on the addition of cholesterol, 12-AS showed significant increases in this parameter with the effect being potentiated at higher temperatures. This difference in behaviour has been attributed to a fluorophore-cholesterol interaction that resulted in a change in the fluorophore geometry. Not only do DPH and 12-AS sense different depolarizing rotations due to the different directions of their emission dipoles but also differ in their lipid interactions which alter their limiting anisotropies. The implication is that the comparison of steady-state anisotropy measurements between chemically identical fluorophores in different lipid environments may be complicated by molecular distortions that change the motions to which the steady-state fluorescence parameters will be sensitive. 相似文献
27.
Recombinant bovine neurokinin-2 receptor stably expressed in Chinese hamster ovary cells couples to multiple signal transduction pathways. 总被引:2,自引:0,他引:2
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H R Eistetter D J Church A Mills P P Godfrey A M Capponi R Brewster M F Schulz E Kawashima S J Arkinstall 《Molecular biology of the cell》1991,2(10):767-779
Neurokinins are a family of neuropeptides with widespread distribution mediating a broad spectrum of physiological actions through three distinct receptor subtypes: NK-1, NK-2, and NK-3. We investigated some of the second messenger and cellular processes under control by the recombinant bovine NK-2 receptor stably expressed in Chinese hamster ovary cells. In this system the NK-2 receptor displays its expected pharmacological characteristics, and the physiological agonist neurokinin A stimulates several cellular responses. These include 1) transient inositol 1,4,5-trisphosphate (IP3) formation and Ca2+ mobilization, 2) increased out put of arachidonic acid and prostaglandin E2 (PGE2), 3) enhanced cyclic AMP (cAMP) generation, 4) increased de novo DNA synthesis, and 5) an induction of the "immediate early" genes c-fos and c-jun. Although NK-2 receptor-mediated IP3 formation involves activation of a pertussis toxin-insensitive G-protein, increased cAMP production is largely a secondary response and can be at least partially attributed to autocrine stimulation by endogenously generated eicosanoids, particularly PGE2. This is the first demonstration that a single recombinant neurokinin receptor subtype can regulate, either directly or indirectly, multiple signal transduction pathways and suggests several potential important mediators of neurokinin actions under physiological conditions. 相似文献
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The similarity transformation approach is used to analyze the structural identifiability of the parameters of a nonlinear model of microbial growth in a batch reactor in which only the concentration of microorganisms is measured. It is found that some of the model parameters are unidentifiable from this experiment, thus providing the first example of a real-life nonlinear model that turns out not to be globally identifiable. If it is possible to measure the initial concentration of growth-limiting substrate as well, all model parameters are globally identifiable. 相似文献
30.
Berardinelli JG Godfrey RW Adair R Lunstra DD Byerley DJ Cardenas H Randel RD 《Theriogenology》1992,37(3):641-654
The objective of this study was to evaluate seasonal changes of cortisol and prolactin (PRL) concentrations in Brahman and Hereford bulls moved to locations that differ in geographical and environmental conditions. Postpubertal Hereford bulls from Montana (n = 15) and Nebraska (n = 15) and Brahman bulls from Texas (n = 18) were located in or relocated to Montana, Nebraska or Texas so that each location had 5 Montana Herefords, 5 Nebraska Herefords and 6 Texas Brahman bulls. Blood samples were collected at 20-minute intervals for 8 hours in November (Fall 1), April (Spring) and November (Fall 2) of the next year. These dates corresponded to 6, 12 and 18 months, respectively, after relocation in May of the first year. Cortisol concentrations were higher (P<0.05) in Fall 1 than in Fall 2 and were higher (P<0.05) for bulls in Montana than for bulls in Texas. The decrease in cortisol concentrations from Fall 1 to Fall 2 was negatively related (P<0.05) to age and weight. There was a three-way interaction (P<0.05) of breed-type origin, location and season for PRL concentrations. Seasonal patterns of PRL concentrations differed between relocated Texas Brahman and Hereford bulls, and patterns for relocated bulls differed from those of the nonrelocated bulls. Seasonal patterns of PRL were influenced to a greater extent by relocation in Texas Brahman bulls than in Hereford bulls. 相似文献