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11.
The phylogenetic distributions ofσ- and phencyclidine receptors in neural tissues of 13 species and the pharmacological characteristics of these receptors in whole sea anemone and neural tissues of the guinea pig, chicken, and frog were studied. Specific binding of [3H]haloperidol and [3H]N-[1-(2-thienyl)cyclohexyl]-3,4-piperidine, ligands that bind with high affinity to σ- and phencyclidine receptors, respectively, was detected in all organisms examined. The order of potencies of various ligands to inhibit 1 nM [3H]haloperidol binding in brains of frogs and guinea pigs or 1 nM [3H]N-[1-(2-thienyl)cyclohexyl]-3,4–piperidine in chicken or guinea pig brain homogenates was very similar. However, the characteristics and stereospecificity of binding of the two radioligands in sea anemone were different than in higher organisms. The results suggest that σ– and phencyclidine binding sites are evolutionarily old, as the characteristics of the two sites are well preserved over a range of vertebrate phyla. 相似文献
12.
Human melanoma cells express a novel integrin receptor for laminin 总被引:11,自引:0,他引:11
This study sought to determine whether human melanoma cells express integrin-related receptors that mediate their adhesion to laminin. We found that antibodies against the integrin beta 1 chain blocked cell attachment to laminin-coated surfaces. Furthermore, immunofluorescence staining demonstrated beta 1 complexes in vinculin-positive focal adhesion plaques on the basal surface of cells attached to laminin substrates. Chromatography of detergent extracts of 125I-surface-labeled cells on laminin-Sepharose columns recovered two major laminin-binding proteins (100 and 130 kDa, reduced) that bound with high affinity to the columns and were eluted with EDTA. Both proteins were specifically immunoprecipitated from column fractions with monoclonal and polyclonal antibodies to the integrin beta 1 subunit, indicating that they form a noncovalent heterodimer complex. The alpha-like subunit is composed of a 30-kDa light chain that is joined by a disulfide bond to the 100-kDa heavy chain. This complex was not recovered from columns of fibronectin- or collagen type I- or IV-Sepharose. Laminin-binding by the alpha beta 1 complex was independent of Arg-Gly-Asp or Tyr-Ile-Gly-Ser-Arg-like sequences, but required the presence of divalent cations. The 100-kDa alpha-like subunit was electrophoretically and immunochemically distinct from the other known alpha subunits, alpha 1-alpha 6. The results indicate that human melanoma cells express a novel laminin-specific integrin beta 1 complex which may mediate the cells' interactions with this ligand. 相似文献
13.
Thiophosphorylation causes Ca2+-independent norepinephrine secretion from permeabilized PC12 cells 总被引:2,自引:0,他引:2
Adenosine-5'-O-(3-thiotriphosphate) (ATP gamma S) was used to examine the role of phosphorylation in the regulation of norepinephrine secretion by digitonin-permeabilized PC12 cells. While most kinases will use ATP gamma S to thiophosphorylate proteins, thiophosphorylated proteins are relatively resistant to dethiophosphorylation by protein phosphatases. Norepinephrine secretion by permeabilized PC12 cells was ATP- and Ca2+-dependent but resistant to calmodulin antagonists. Half-maximum secretion was obtained in 0.75 microM Ca2+. Permeabilized PC12 cells were incubated with ATP gamma S in the absence of Ca2+, the ATP gamma S was removed, and norepinephrine secretion was determined. Preincubation with ATP gamma S increased the amount of norepinephrine secreted in the absence of Ca2+, but it had no effect on the amount released in the presence of Ca2+. After a 15-min preincubation in 1 mM ATP gamma S, there was almost as much secretion in the absence of Ca2+ as in its presence. Inclusion of ATP in the preincubation inhibited the effect of ATP gamma S. Ca2+ stimulated the rate of modification by ATP gamma S as brief preincubations with ATP gamma S in the presence of Ca2+ resulted in higher levels of Ca2+-independent secretion than did preincubations with ATP gamma S in the absence of Ca2+. Similarly, brief preincubations of permeabilized cells with ATP in the presence of Ca2+ resulted in elevated levels of Ca2+-independent secretion. Secretion of norepinephrine from ATP gamma S-treated cells was ATP-dependent. These results suggest that norepinephrine secretion by PC12 cells is regulated by a Ca2+-dependent phosphorylation. Once this phosphorylation has occurred, secretion is still ATP-dependent, but it no longer requires Ca2+. 相似文献
14.
Y Suzuki W Wang T H Vu T A Raffin 《Biochemical and biophysical research communications》1992,184(3):1339-1343
Neutrophil adherence to endothelium is partially mediated by the expression of endothelial leukocyte adhesion molecule-1 (ELAM-1) on endothelial cells activated by agents such as lipopolysaccharide (LPS) and phorbol myristate acetate (PMA). To elucidate molecular mechanisms involved in the induction of ELAM-1 on endothelial cells, we investigated the effect of the NADPH oxidase inhibitor, apocynin (4-hydroxy-3-methoxyacetophenone), on ELAM-1 mRNA expression in human umbilical vein endothelial cells (HUVEC) by Northern blot analysis. Apocynin downregulated both LPS- and PMA-induced ELAM-1 mRNA expression in a dose-dependent manner. Our results suggest NADPH oxidase might play a key role in ELAM-1 mRNA expression in HUVEC. 相似文献
15.
I. I. Pottosin P. R. Andjus D. Vučelić G. N. Berestovsky 《The Journal of membrane biology》1993,136(2):113-124
We studied the effects of H2O/D2O substitution on the permeation and gating of the large conductance Ca2+-activated K+ channels inChara gymnophylla droplet membrane using the patchclamp technique. The selectivity sequence of the channel was: K+>Rb+≫Li+, Na+, Cs+ and Cl−. The conductance of this channel in symmetric 100mm KCl was found to be 130 pS. The single channel conductance was decreased by 15% in D2O as compared to H2O. The blockade of channel conductance by cytosolic Ca2+ weakened in D2O as a result of a decrease in zero voltage Ca2+ binding affinity by a factor of 1.4. Voltage-dependent channel gating was affected by D2O primarily due to the change in Ca2+ binding to the channel during the activation step. The Hill coefficient for Ca2+ binding was 3 in D2O and around 1 in H2O. The values of the Ca2+ binding constant in the open channel conformation were 0.6 and 6 μm in H2O and D2O, respectively, while the binding in the closed conformation was much less affected by D2O. The H2O/D2O substitution did not produce a significant change in the slope of channel voltage dependence but caused a shift as large
as 60 mV with 1mm internal Ca2+. 相似文献
16.
Allen R. Rhoads Rabin Parui Ngoc-Diep Vu Robert Cadogan Paul D. Wagner 《Journal of neurochemistry》1993,61(5):1657-1666
Abstract— Secretion of catecholamines by rat PC12 cells is strongly stimulated by extracellular ATP via a P2 -type pur-inergic receptor. ATP-induced norepinephrine release was inhibited 80% when extracellular Ca2+ was absent. Only four nucleotides, ATP, ATPγS, benzoylbenzoyl ATP (BzATP), and 2-methylthio-ATP, gave substantial stimulation of norepinephrine release from PC12 cells. ATP-induced secretion was inhibited by Mg2+ , and this inhibition was overcome by the addition of excess ATP suggesting that ATP4- was the active ligand. ATP-induced secretion of catecholamine release was enhanced by treatment of cells with pertussis toxin or 12- O -tetradecanoylphorbol 13-acetate. The stimulatory effects of 12- O -tetradecanoyl-phorbol 13-acetate and pertussis toxin on norepinephrine release were additive. After brief exposure of intact cells to the photoaffinity analog, [α-32 P]BzATP, two major proteins of 44 and 50 kDa and a minor protein of 97 kDa were labeled. An excess of ATP-γS and BzATP but not GTP blocked labeling of the proteins by [32 P]BzATP. Labeling of the 50-kDa protein was more sensitive to competition by 2-methylthio-ATP than the other labeled proteins, suggesting that the 50-kDa protein represents the P2 receptor responsible for ATP-stimulated secretion in these cells. 相似文献
17.
T cell receptor-beta mRNA splicing: regulation of unusual splicing intermediates. 总被引:10,自引:3,他引:7 下载免费PDF全文
L Qian L Theodor M Carter M N Vu A W Sasaki M F Wilkinson 《Molecular and cellular biology》1993,13(3):1686-1696
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Bui Hai Ninh Duong Thi Dung Bui Huu Tai Pham Hai Yen Nguyen Xuan Nhiem Truong Thi Thu Hien Do Thi Trang Nguyen Van Tuyen Le Tuan Anh Nguyen Thi Hoai Phan Van Kiem 《化学与生物多样性》2023,20(3):e202201048
A new isopropyl chromone ( 1 ) and a new flavanone glucoside ( 2 ) together with eleven known compounds ( 3–13 ) were isolated from the leaves of Syzygium cerasiforme (Blume) Merr. & L.M.Perry. Their structures were elucidated as 5,7-dihydroxy-2-isopropyl-6,8-dimethyl-4H-chromen-4-one ( 1 ), 5,7-dihydroxyflavanone 7-O-β-D-(6′′-O-galloylglucopyranoside) ( 2 ), strobopinin ( 3 ), demethoxymatteucinol ( 4 ), pinocembrin-7-O-β-D-glucopyranoside ( 5 ), (2S)-hydroxynaringenin-7-O-β-D-glucopyranoside ( 6 ), afzelin ( 7 ), quercetin ( 8 ), kaplanin ( 9 ), endoperoxide G3 ( 10 ), grasshopper ( 11 ), vomifoliol ( 12 ), litseagermacrane ( 13 ) by the analysis of HR-ESI-MS, NMR, and CD spectral data. Compounds 1 , 2 , 5 , 6 and 10 inhibited NO production on LPS-activated RAW264.7 cells with IC50 values of 12.28±1.15, 8.52±1.62, 7.68±0.87, 9.67±0.57, and 6.69±0.34 μM, respectively, while the IC50 values of the other compounds ranging from 33.38±0.78 to 86.51±2.98 μM, compared to that of the positive control, NG-monomethyl-L-arginine acetate (L-NMMA) with an IC50 value of 32.50±1.00 μM. 相似文献