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  • Articles  (5)
  • Articles: DFG German National Licenses  (5)
  • 1995-1999  (5)
  • 1996  (5)
  • 1
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] EPR-1 is an activation-dependent molecule of relative molecular mass 62,000 (Mr 62K) which participates in protease-depen-dent mechanisms of lymphocyte co-stimulation8'9. Anti-EPR-1 mAb 2E1 (ref. 8) nearly completely inhibited lymphocyte proliferation in vitro that was stimulated by soluble or ...
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  • 2
    ISSN: 1432-1912
    Keywords: Somatostatin ; BIM-23027 ; Rat colonic mucosa ; sst2 receptors ; SRIF-binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have previously shown that the somatostatin (SRIF) sst2 receptor-selective peptide, BIM-23027, is a potent antisecretory agent in rat isolated distal colonic mucosa (RDCM) and in radioligand binding studies in RDCM membranes, it only maximally inhibited approximately 40% of [125I]-Tyr11-SRIF-14 binding (McKeen ES, Feniuk W, Humphrey PPA (1995) Naunyn-Schmiedeberg's Arch Pharmacol 352:402–411). The aim of this study was to characterise the BIM-23027-sensitive and -insensitive SRIF binding sites in more detail and to compare their properties with those of the recombinant sst2 receptor stably expressed in mouse fibroblast (Ltk−) cells. SRIF-14, SRIF-28, CGP-23996 and D Trp8-SRIF-14 abolished [125I]-Tyr11-SRIF-14 binding (pIC50 values, 8.7–9.7) but the competition curves had Hill slopes which were less than unity. Octreotide and L-362,855 inhibited binding over a wide concentration range (0.1 nM-1 μM) and inhibition of binding was incomplete at the highest concentration studied. BIM-23056 (PIC50 〈6.5) was a weak inhibitor of [125]-Tyr11-SRIF-14 binding. GTPγS decreased [125I]-Tyr11-SRIF-14 binding by 40%. Further binding experiments with [125I]-Tyr11-SRIF-14 were carried out in RDCM in the continuous presence of BIM-23027 (1 μM). Under these conditions, seglitide had no effect on [125I]-Tyr11-SRIF-14 binding at concentrations up to 10 μM, whilst SRIF-14 and SRIF-28 abolished specific [125I]-Tyr11-SRIF-14 binding in a manner which was consistent with the ligand binding to two sites. SRIF-14 and SRIF-28 displayed high affinity (pIC50 values of 9.8 and 9.3 respectively) for approximately 70% of these binding sites and low affinity (pIC50 values of 7.8 and 7.3) for the remaining sites. Octreotide, L-362,855 and BIM-23056 were weak inhibitors of [125I]-Tyr11-SRIF-14 binding (PIC50 〈6.5). [125I]-BIM-23027 labelled a single population of SRIF binding sites in RDCM membranes and mouse fibroblast (Ltk−) cells stably expressing the human recombinant sst2 receptor. There was a significant correlation between the affinitestimates of a range of SRIF analogues at inhibiting [125I]-BIM-23027 binding in RDCM membranes and binding to the recombinant sst2 receptor in Ltk− cells, suggesting that the sites labelled by [125I]-BIM-23027 in RDCM are similar to the sst2 receptor. GTPγS (100 μM) decreased [125I]-BIM-23027 binding in RDCM by 60%. The results from these studies demonstrate that [125I]-Tyr11-SRIF-14 labels a heterogeneous population of high affinity SRIF binding sites in RDCM membranes. The majority of these sites are insensitive to GTPγS and display negligible affinity for the cyclic hexapeptides, BIM-23027 and seglitide. The remaining high affinity binding sites can be selectively labelled with [125I]-BIM-23027, are sensitive to GTPγS and show similar characteristics to the recombinant sst2 receptor which appears to mediate the antisecretory effects of SRIF in the mucosa (McKeen ES, Feniuk W, Humphrey PPA (1995) Naunyn-Schmiedeberg's Arch Pharmacol 352:402–411).
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  • 3
    ISSN: 1432-1912
    Keywords: Key words Somatostatin ; BIM-23027 ; Rat colonic mucosa ; sst2 receptors ; SRIF-binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have previously shown that the somatostatin (SRIF) sst2 receptor-selective peptide, BIM-23027, is a potent antisecretory agent in rat isolated distal colonic mucosa (RDCM) and in radioligand binding studies in RDCM membranes, it only maximally inhibited approximately 40% of [125I]-Tyr11-SRIF-14 binding (McKeen ES, Feniuk W, Humphrey PPA (1995) Naunyn-Schmiedeberg‘s Arch Pharmacol 352:402–411). The aim of this study was to characterise the BIM-23027-sensitive and -insensitive SRIF binding sites in more detail and to compare their properties with those of the recombinant sst2 receptor stably expressed in mouse fibroblast (Ltk–) cells. SRIF-14, SRIF-28, CGP-23996 and D Trp8-SRIF-14 abolished [125I]-Tyr11-SRIF-14 binding (pIC50 values, 8.7–9.7) but the competition curves had Hill slopes which were less than unity. Octreotide and L-362,855 inhibited binding over a wide concentration range (0.1 nM-1 μM) and inhibition of binding was incomplete at the highest concentration studied. BIM-23056 (pIC50 〈6.5) was a weak inhibitor of [125]-Tyr11-SRIF-14 binding. GTPγS decreased [125I]-Tyr11-SRIF-14 binding by 40%. Further binding experiments with [125I]-Tyr11-SRIF-14 were carried out in RDCM in the continuous presence of BIM-23027 (1 μM). Under these conditions, seglitide had no effect on [125I]-Tyr11-SRIF-14 binding at concentrations up to 10 μM, whilst SRIF-14 and SRIF-28 abolished specific [125I]-Tyr11-SRIF-14 binding in a manner which was consistent with the ligand binding to two sites. SRIF-14 and SRIF-28 displayed high affinity (pIC50 values of 9.8 and 9.3 respectively) for approximately 70% of these binding sites and low affinity (pIC50 values of 7.8 and 7.3) for the remaining sites. Octreotide, L-362,855 and BIM-23056 were weak inhibitors of [125I]-Tyr11-SRIF-14 binding (pIC50 〈6.5). [125I]-BIM-23027 labelled a single population of SRIF binding sites in RDCM membranes and mouse fibroblast (Ltk–) cells stably expressing the human recombinant sst2 receptor. There was a significant correlation between the affinity estimates of a range of SRIF analogues at inhibiting [125I]-BIM-23027 binding in RDCM membranes and binding to the recombinant sst2 receptor in Ltk– cells, suggesting that the sites labelled by [125I]-BIM-23027 in RDCM are similar to the sst2 receptor. GTPγS (100 μM) decreased [125I]-BIM-23027 binding in RDCM by 60%. The results from these studies demonstrate that [125I]-Tyr11-SRIF-14 labels a heterogeneous population of high affinity SRIF binding sites in RDCM membranes. The majority of these sites are insensitive to GTPγS and display negligible affinity for the cyclic hexapeptides, BIM-23027 and seglitide. The remaining high affinity binding sites can be selectively labelled with [125I]-BIM-23027, are sensitive to GTPγS and show similar characteristics to the recombinant sst2 receptor which appears to mediate the antisecretory effects of SRIF in the mucosa (McKeen ES, Feniuk W, Humphrey PPA (1995) Naunyn-Schmiedeberg‘s Arch Pharmacol 352:402–411).
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  • 4
    ISSN: 1432-1912
    Keywords: Key words45Ca2+ influx ; PC12 cells ; P2 purinoceptors ; Ion channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of this study was to determine whether 45Ca2+ influx could be used as a quantitative measure of channel activation for functional characterisation of P2X purinoceptors in cell lines. In undifferentiated PC12 cells, grown in suspension, ATP (EC50 = 45 μM), ATPγS (EC50 = 50 μM) and 2-meSATP (EC50 = 81 μM) but not ab meATP (1 mM) stimulated 45Ca2+ influx 2–5 fold. This effect did not appear to be due to activation of P2U or P2Y purinoceptors since 1 mM UTP, ADP or ADPβS did not produce any significant effect. Similarly, the effects of ATP were not apparently mediated through activation of P2Z purinoceptors since dibenzylATP behaved as a weak (EC50 = 191 μM) partial agonist (Maximal effect 29.5% of ATP maximum) and there was no detectable ATP-stimulated ethidium bromide uptake in the PC12 cells. ATP-stimulated 45Ca2+ influx was not affected by nifedipine suggesting that it was not secondary to activation of L-type calcium channels and rather reflected influx through a P2X purinoceptor present in these cells. The ATP-stimulated 45Ca2+ influx could be reduced by monovalent cations, presumably as a result of direct competition for influx through the cation channel, with the following rank order of potency :- guanidinium (EC50 = 16 mM) 〉 sodium 〉 Tris 〉 choline 〉 N-methyl-D-glucamine = sucrose). A number of P2 purinoceptor antagonists inhibited ATP-stimulated 45Ca2+ influx. Pyridoxalphosphate-6-azophenyl-2′,4′-disulphonic acid (3–300 μM), pyridoxal 5-phosphate (3–300 μM) and d-tubocurarine (30–300 μM) produced an insurmountable antagonism of responses to ATP, with no marked change in agonist EC50. Suramin (100–300 μM) and cibacron blue (30–300 μM) produced a surmountable antagonism while DIDS (4,4′-diisothiocyanatostilbene-2,2′disulfonic acid) only antagonised responses to ATP at concentrations in excess of 300 μM. The general properties of the P2X purinoceptor population identified in these cells were consistent with them being P2X2 purinoceptors. These findings suggest that ATP-stimulated 45Ca2+ influx may be used as a reliable and quantitative functional assay for characterisation of P2X purinoceptor subtypes in cell lines.
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  • 5
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A poly(vinyl chloride) (PVC)/poly(methyl methacrylate) (PMMA) (80/20 w/w) polymer blend was studied by mechanical spectroscopy. Two relaxations can be distinguished: in the glassy state, a very large secondary relaxation in the range of 100 K to 325 K which results from the combination of secondary relaxations of PVC and PMMA; and only one main relaxation at 364 K associated to the glass rubber transition. The relaxation spectrum in the range of the β relaxation has been described by a relaxation time distribution function based upon a Gaussian function and a series-parallel model. The α relaxation was studied by means of a theoretical approach for the nonelastic deformation of polymers. We found that the miscibility of this blend appears to be a function of the observation scale: the PVC/PMMA blend is heterogeneous at the scale of molecular movements involved for the β relaxation process but homogeneous at the scale of the chain segments responsible for the α relaxation dynamics. © 1996 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
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