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161.
162.
Uptake, release and metabolism of docosahexaenoic acid (DHA, c22:6 omega 3) in human platelets and neutrophils 总被引:5,自引:0,他引:5
S Fischer C von Schacky W Siess T Strasser P C Weber 《Biochemical and biophysical research communications》1984,120(3):907-918
Exogenous DHA is converted by human platelets to 14- and 11- HDHE and by human neutrophils mainly to 7- HDHE . Human platelets prelabeled with 14C-DHA, 14C-EPA and 14C-AA and stimulated with thrombin release and metabolize DHA only in trace amounts as compared to EPA and AA. 14C-DHA is incorporated into the 2-position of platelet phospholipids and occurs predominantly in phosphatidylethanolamine. DHA and EPA were also incorporated by dietary means into phospholipids of platelets and neutrophils. In resting platelets free DHA as well as free AA and EPA are not detectable. In platelets stimulated ex vivo with thrombin DHA is not significantly released which is in contrast to EPA and AA. After stimulation, 14- HDHE is found only in trace amounts as compared to 12-HETE and 12- HEPE . In DHA enriched neutrophils formation of HDHEs cannot be demonstrated after stimulation with ionophore A 23187. We conclude that even after dietary enrichment of DHA in phospholipids of platelets and neutrophils the level of free DHA and/or formation of HDHEs might be too low to substantially affect arachidonic acid metabolism and related functions of these cells. 相似文献
163.
Casein kinase II (CKII) activity is enhanced as much as 2–3 fold in established and 4–5-fold in transformed human cell lines when compared to that of fibroblasts and primary human tumour cell cultures where CKII activity never exceeded a basic level. The high activity of CKII in transformed cells and in established cell lines was reduced to about the same basic level after treatment with heparin, a highly specific inhibitor of CKII activity. The activity of the cAMP-dependent protein kinase was virtually the same in fibroblasts and various human tumour cell lines investigated. 相似文献
164.
Hahn H. L.; Wilson A. G.; Graf P. D.; Fischer S. P.; Nadel J. A. 《Journal of applied physiology》1978,44(2):144-149
165.
Shen K. Yang Harry V. Gelboin John D. Weber V. Sankaran Daniel L. Fischer James F. Engel 《Analytical biochemistry》1977
The optical isomers of (±)r-7,t-8-dihydroxy-7,8-dihydrobenzo[a]pyrene and its synthetic precursor (±)r-7,t-8-dihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene were resolved as their di-(−)menthoxyacetates using high-pressure liquid chromatography. Saponification of the resolved diesters yielded the corresponding enantiomers. The specific rotation, CD spectra, and ORD curves are reported. The resolution of these optical isomers permits detailed studies on the enzymatic intermediates and the mechanism of benzo[a]pyrene activation to its carcinogenic form. The method is of general usefulness for the resolution of optical isomers. 相似文献
166.
Chemical analysis of Melampodium americanum yielded, besides the known melampodinin A, four new melampolides, melampodinin B, melampodinin C, 9-des 相似文献
167.
The covalent hydration of β-halopyruvic acids and β-halopyruvamides has been investigated in the uv region by stopped-flow techniques. In aqueous solutions of β-bromopyruvate and related compounds, the geminal diol is the predominant form at all pH values. Kinetic investigations have also been carried out on these hydrations. General bases enhance the rate of approaching the equilibrium. Specific acid catalysis was not detected. In the water-catalyzed reaction of pyruvamides, the relationship between the equilibrium constants K and the rate constants of the forward reaction
shows that the transition state is more productlike. 相似文献
168.
Uptake rates of L-alanine, L-serine and L-aspartate and trans-membrane electrical potentials (Δψ) were determined for a pH range in the external medium between 3.5 and 9.0. The proton electrochemical gradients ( ) were calculated from Δψ, pH of the medium, and an assumed cytoplasmic pH of 7.5. At external amino-acid concentrations of 0.1 mol m−3 , where carrier-mediated uptake dominates total uptake, a linear correlation between uptake rates and is obtained, which extrapolates to zero uptake at zero . This corroborates the contention that neutral and acidic amino acids are taken up by Lemna gibba L. by H+ -cotransport. 相似文献
169.
Membrane Potential Changes Related to Active Transport of Glycine in Lemna gibba G1 总被引:5,自引:5,他引:0
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Accumulation of 14C-labeled glycine and microelectrode techniques were employed to study glycine transport and the effect of glycine on the membrane potential (Δψ) in Lemna gibba G1. Evidence is presented that two processes, a passive uptake by diffusion and a carrier-mediated uptake, are involved in glycine transport into Lemna cells. At the onset of active glycine uptake the component of Δψ which depended on metabolism was decreased. The depolarized membrane repolarized in the presence of glycine. This glycine-induced depolarization followed a saturation curve with increasing glycine concentration which corresponded to carrier-mediated glycine influx kinetics. The transport of glycine was correlated with the metabolically dependent component of Δψ. It is suggested (a) that the transient change in Δψ reflects the operation of an H+-glycine cotransport system driven by an electrochemical H+ gradient; and (b) that this system is energized by an active H+ extrusion. Therefore the maximum depolarization of the membrane consequently depended on both the rate of glycine uptake and the activity of the proton extrusion pump. 相似文献
170.
ATP-depleted human red cells have been incubated in a glucose-containing medium with [32P]orthophosphate in the presence and in the absence of cyclic 3',5'-AMP and dibutyril cyclic 3',5'-AMP. Spectrin, pyruvate kinase, phosphofructokinase, glucose-6-phosphate dehydrogenase and hemoglobin A1 have been purified and analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Protein-bound radioactivity has been measured from the sodium dodecyl sulfate polyacrylamide gels and the trichloroacetic acid-precipitated proteins. In the cytosol, the most intense phosphorylation was found for pyruvate kinase whose, in the presence of cyclic AMP, specific radioactivity was comparable to that of the membrane protein and spectrin. In the absence of cyclic nucleotides it was five times less phosphorylated. Phosphofructokinase was only phosphorylated when the red cells were incubated with cyclic nucleotides; the extent of phosphorylation was four times less than for pyruvate kinase. Hemoglobin, glucose-6-phosphate dehydrogenase and a contaminant protein copurified with phosphofructokinase were not phosphorylated: the 'background' of the radioactivity found for these proteins was 100 times less than for pyruvate kinase and spectrin, and 20 times less than for phosphofructokinase (+cyclic AMP). 相似文献