bluuebunny/crossref_metadata_2025_split huggingface dataset:
A unique pool of free arachidonate serves as substrate for both cyclooxygenase and lipoxygenase in platelets
Authors: Chevy Françoise , Wolf Claude , Colard Odile 
Published: February 2007

AbstractStimulation of platelets induces a rapid release of arachidonate from specific phospholipids and subsequent remodeling of arachidonate‐containing phospholipids. This process is accompanied by transformation of released arachidonate by cyclooxygenase and lipoxygenase enzymes. We addressed the question of whether the cyclooxygenase and the lipoxygenase products originated from the same arachidonate‐containing phospholipids. [14C]Arachidonate prelabeled platelets were stimulated by thrombin or by ionophore A 23187. We monitored the cyclooxygenase pathway by following 12‐hydroxy‐5,8,10‐heptadecatrienoic acid [12(S)‐HHT] formation and the lipoxygenase pathway by following 12‐hydroxy‐5,8,10,14‐eicosatetraenoic acid [12(S)‐HETE] formation and compared specific activities. The data showed that the same pool of released arachidonate can be utilized by either cyclooxygenase or by lipoxygenase. Indeed, the specific activity of both products was identical when both enzymes were acting. Since cyclooxygenase was rapidly deactivated while lipoxygenase continued to be active, the specific activity of 12(S)‐HETE became lower than the specific activity of 12(S)‐HHT when large amounts of 12(S)‐HETE were synthesized. Based on comparison of specific activity between phospholipids and oxygenated products, the pools of arachidonate‐containing phospholipids involved in the synthesis of oxygenated products are dependent on the amount of arachidonate released.
Paf‐acether in human skin
Authors: Denizot Yves , Michel Laurence , Benveniste Jacques , Meybeck Alain , Thomas Yolène , Duberfret Louis 
Published: February 2007

AbstractPaf is a phospholipid mediator present in human skin which induces inflammatory events such as neutrophil infiltration and increased vascular permeability. Recent data suggest that cutaneous cells, such as fibroblasts and keratinocytes, produce paf and that paf is released during allergic cutaneous reactions. It is tempting to speculate that paf may contribute to the development of various skin disorders with acute and chronic skin inflammation. Paf antagonists may help in bringing answers to this hypothesis and may offer new prospects for the treatment of cutaneous inflammatory diseases.
Effect of platelet‐activating factor on cortisol and corticosterone secretion by perfused dog adrenal
Authors: Aikawa Tadaomi , Hirose Taeko , Matsumoto Itsuro , Morikawa Toshiko , Shimada Toshio , Mine Yumi , Tsujimoto Yoshiki , Tsuji Yoshiro 
Published: February 2007

AbstractAdministration of platelet‐activating factor (PAF) to perfused adrenal increased cortisol and corticosterone secretion. With hexadecyl PAF (C16PAF; 1‐O‐hexadecyl‐2‐acetyl‐sn‐glycero‐3‐phosphocholine), the increase was significant at 1 nM and maximal at 10 nM. The responses to 10 nM octadecyl PAF (C18PAF; 1‐O‐octadecyl‐2‐acetyl‐sn‐glycero‐3‐phosphocholine) were one fourth of those to 10 nM C16PAF. The addition of C16PAF to dispersed adrenal cells significantly increased cortisol and corticosterone production at 0.1 nM and 10 nM, respectively. C16PAF was about 1000 times more potent than histamine on a molar basis in respect to cortisol response in both perfused adrenal and dispersed adrenal cells. The results suggest that PAF induces cortisol release from dog adrenal.
Radioimmunoassay for platelet‐activating factor
Authors: Karasawa Ken , Satoh Noriko , Hongo Toshio , Nakagawa Yasuhito , Setaka Morio , Nojima Shoshichi 
Published: February 2007

AbstractA radioimmunoassay (RIA) for measurement of platelet‐activating factor (PAF) was developed. At a final antiserum dilution of 1∶640, the lowest detection limit of PAF was 0.1 pmol (50 pg). The standard curve obtained was suitable for measurement of PAF in amounts ranging from 0.1 pmol to 30 pmol. The antiserum showed high specificity. Cross‐reaction for lysoPAF, lysophosphatidylcholine and long‐chain phosphati‐dylcholines was very low (less than 0.025%). 1‐Palmitoyl‐2‐acetyl‐sn‐glycero‐3‐phosphocholine cross‐reacted slightly (6.25%). PAF exogenously added to macrophage suspensions was quantitatively determined by RIA after solvent extraction and high‐performance liquid chromatographic separation. RIA was also used to estimate PAF formation after stimulation of rabbit alveolar macrophages in suspension with calcium ionophore A23187.
Synthesis of a PAF immunogen and production of PAF‐specific antibodies
Authors: Smal Mary A. , Baldo Brian A. , Redmond John W. 
Published: February 2007

AbstractPlatelet activating factor (PAF), a naturally occurring phospholipid with many potent physiological and pharmacological activities, is implicated as a mediator of many diseases. An immunoassay for PAF would greatly improve quantitation, and hence PAF‐specific antibodies were required. Chemically‐reactive analogs of PAF, containing an aldehyde group at the end of the 1‐O‐alkyl chain (hexyl or dodecyl), were synthesized from readily available materials. During the multi‐step synthetic procedure, the aldehyde group was protected as an acetal, which was converted by mild acidic hydrolysis to the aldehyde immediately prior to protein coupling. These analogs were coupled to methylated bovine serum albumin and the resultant conjugates were injected into rabbits. Antibodies to PAF were detected using a solid phase radioimmunoassay based on Protein A‐Sepharose. The dodecyl PAF conjugate proved to be the more immunogenic conjugate with more than half of the rabbits producing significant levels of antibodies (at least a 10‐fold increase in radioactive uptake over pre‐immune levels). Results from solid phase immunoassays employing nitrocellulose discs impregnated with PAF, lysoPAF, lecithin, lysolecithin and 2‐O‐methyl‐lysoPAF indicated that the antibodies recognized only PAF. PAF‐specific antibodies were isolated by affinity chromatography using a column of PAF‐poly(lysine) conjugated to carboxy‐activated polyacrylamide. The antibodies may be employed in a sensitive and specific immunoassay for PAF and for many other studies involving PAF.
A specific, sensitive and high‐capacity immunoassay for PAF
Authors: Baldo Brian A. , Smal Mary A. , McCaskill Alistair C. 
Published: February 2007

AbstractA specific radioimmunoassay for platelet‐activating factor (PAF) sensitive in the range 10–1000 pg (0.02–2 pmoles) has been developed. Detailed quantitative hapten inhibition studies showed specificity for the acetyl group at C‐2 of PAF, a requirement for the ether linkage at C‐1 and some tolerance for substituents on the choline nitrogen. No significant cross‐reactivity was found with phosphatidylcholine and lysophosphatidylcholine or with lysoPAF.
Inhibitor(s) of platelet‐activating factor (PAF) in human saliva
Authors: Smal Mary A. , Baldo Brian A. 
Published: February 2007

AbstractQuantitation of platelet‐activating factor (PAF) in human saliva samples by radioimmunoassay indicated there was, at times, sufficient PAF present to aggregate platelets. However, in certain samples, we observed little or no aggregation, and furthermore, these samples were found to inhibit aggregation induced by PAF (200 pg). Chromatographic fractionation of pooled saliva increased the PAF activity 4‐fold, and the observed inhibitory activity was found to co‐migrate with the fatty acids. The inhibitory fraction was found to be active against platelet aggregation induced by arachidonic acid (3.4 nmole) as well as PAF (25 pg), but not thrombin (20 mU). These results indicate the existence of a PAF inhibitor in saliva, which may explain why potentially toxic levels of PAF can occur in the saliva of normal, healthy individuals. These findings also highlight an important advantage of the radioimmunoassay over platelet aggregation for the quantitation of PAF in, at least, some biological fluids.
L‐659,989: A useful probe in the detection of multiple conformational states of PAF receptors
Authors: Hwang San‐Bao , Lam My‐Hanh 
Published: February 2007

AbstractL‐659,989 is a potent, specific and competitive plateletactivating factor (PAF) receptor antagonist. The 2,5‐tritium labeled L‐659,989, similar to [3H]PAF, specifically binds to rabbit platelet membranes with an equilibrium dissociation constant (KD) of 1.60 (±0.20) nM in 10 mM MgCl2. However, guanosine 5′‐triphosphate (GTP) and several cations affect the specific binding of [3H]PAF and of [3H]L‐659,989 to rabbit platelet membranes in different ways. K+, Mg2+, Ca2+ and Mn2+ potentiate the specific binding of both ligands. Na+ and Li+ inhibit the specific [3H]PAF binding, but enhance the binding of [3H]L‐659,989; GTP reduces the [3H]PAF binding but has no effect on the binding of [3H]‐L‐659,989. Ni2+ inhibits the [3H]L‐659‐989 binding, but has no effect on the binding of [3H]PAF. In the presence of 150 mM NaCl, [3H]L‐659,989 exhibits identical KD and detectable binding sites (Bmax) values as those in the presence of 10 mM MgCl2, while Kd And Bmax values of [3H]PAF are dramatically reduced in the presence of 150 mM NaCl compared to those in 10 mM MgCl2. These results suggest the existence of multiple conformational states of the PAF specific receptor and that PAF and L‐659,989 bind differently to those states. In the presence of 150 mM NaCl and 1 mM GTP, receptors appear to exist in a single conformational state with an equilibrium dissociation constant (KB) of 0.93 μM for PAF as derived from the Schild plot. In isolated rabbit platelets pretreated with 10 μM ETH 227, a Na+‐specific ionophore, the detectable [3H]PAF binding sites drop from 260 to 100 binding sites per platelet, but the binding sites for [3H]L‐659,989 remain roughly the same. The Na+ binding sites which modulate the conformation of PAF receptors are therefore protected from extracellular Na+ until ionophore is added, and are probably located on the cytoplasmic side of the plasma membrane.
PAF receptor and “cache‐oreilles” effect. Simple PAF antagonists
Authors: Lamotte‐Brasseur J. , Heymans F. , Dive G. , Lamouri A. , Batt J. P. , Redeuilh C. , Hosford D. , Braquet P. , Godfroid J. J. 
Published: February 2007

AbstractNine simple and structurally flexible PAF antagonists were synthesized and their inhibitory effects on PAF induced platelet aggregation were measured. Compounds with PAF antagonistic activity exhibited a negative electrostatic potential generated by two trimethoxyphenyl groups (isocontour at −10 Kcal/mole) at various distances between the negative clouds. The optimal distance between the atoms generating the “cache‐oreilles” system for exhibiting potent PAF antagonistic activity is estimated to be 11–13 Å. In the flexible molecules studied, the dispersion of the electronic distribution is not necessarily favorable for anti‐PAF activity. The data support the simple bipolarized model for the PAF receptor that has been proposed by the authors.
PAF inhibitory activity of diketopiperazines: Structure‐activity relationships
Authors: Shimazaki Norihiko , Shima Ichiro , Okamoto Masanori , Yoshida Keizo , Hemmi Keiji , Hashimoto Masashi 
Published: February 2007

AbstractFR900452, a natural product isolated from the culture broth ofStreptomyces phaeofaciens No. 7739, was found to inhibit PAF‐induced rabbit platelet aggregation with an IC50 of 3.7×10−7M. FR900452, 1‐methyl‐3‐[1‐[5‐methylthiomethyl‐6‐oxo‐3‐(2‐oxo‐3‐cyclopenten‐1‐ylidene)‐2‐piperazinyl]ethyl]‐2‐indoline, has an oxocylopentylidene group incorporated as a vinylogous amide in a diketopiperazine skeleton. This unique structure led us to synthesize diketopiperazine derivatives, 3‐arylalkyl‐6‐substituted‐piperazine‐2,5‐diones. their observed PAF inhibitory activity suggest that the D‐D configuration of diketopiperazine is an important factor for anti‐PAF activity and that the hydrophobic aromatic portion may play a specific role in the binding of the diketopiperazine to the PAF receptor.
Platelet‐activating factor (PAF) receptor antagonists inhibit arachidonic acid induced platelet aggregation in rabbit whole blood
Authors: Ammit Alaina Jean , O'Neill Chris 
Published: February 2007

AbstractThe potency of several platelet‐activating factor (PAF) receptor antagonists was measured by observing their inhibitory effects against PAF induced platelet aggregation. Their selectivity was assessed by monitoring their effect on platelet aggregation induced by arachidonic acid (AA) and adenosine diphosphate (ADP). The antagonists inhibited platelet aggregation induced at the PAF EC50 (0.023 μM) with the following rank order of potency: WEB 2086> WEB 2170> SRI 64–412> SRI 63–675> BN 52021>kadsurenone> SRI 63–441> alprazolam. While the antagonists had no inhibitory effect at the EC50 for ADP (10 μM), they did inhibit platelet aggregation induced at the EC50 for AA (55 μM). However, there was considerable variability in the slope of the inhibitory response and the relative potency of each antagonist against PAF induced platelet aggregation as compared to AA induced platelet aggregation. The antagonist IC50 (μM) against PAF and AA were as follows, with those that showed significantly different (p<0.01) slopes indicated by an asterisk: SRI 63‐441* (3.8, 15.1); SRI 63‐675 (1.4, 36.2); SRI 64‐412 (0.5, 10.5); BN 52021* (2.4, 58.9); kadsurenone* (2.8, 28.3); alprazolam* (10, 25); WEB 2086 (0.055, 0.220), and WEB 2170 (0.107, 0.534). Therefore, in rabbit whole blood the antagonists were potent, although not completely selective, inhibitors of PAF induced platelet aggregation. These results suggest that the mode of action of PAF and AA induced platelet aggregation may share some common features. However, since the slope of the inhibitory response against PAF and AA for some antagonists differed, mechanistic differences in their action appear to exist.
Biological response of guinea pig peritoneal macrophages to platelet‐activating factor
Authors: Hayashi Hidetoshi , Kudo Ichiro , Nojima Shoshichi , Inoue Keizo 
Published: February 2007

AbstractWe investigated the effects of platelet‐activating factor (PAF) on guinea pig peritoneal macrophages. Specific and high‐affinity binding sites for PAF were detected on guinea pig peritoneal macrophages. Scatchard analysis of PAF binding revealed high affinity binding sites (7.9×104/cell) with a dissociation constant of 2.3×10−10 M. When treated with 10−9−10−5 M PAF, guinea pig peritoneal macrophages released hydrogen peroxide into the medium in a time‐dependent manner. The release reaction upon stimulation with 10−5 M PAF reached a plateau within 30 min and the extent of release was twice as high as that when stimulated byN‐formyl‐L‐methionyl‐leucyl‐L‐phenylalanine (fMLP; 2 μM)‐treated cells. Neither lysoPAF nor the PAF enantiomer was effective. PAF‐induced H2O2 release was inhibited specifically by PAF antagonists, suggesting that PAF activated macrophages through binding to specific sites. Lysosomal enzyme (N‐acetyl‐β‐D‐glucosaminidase) was released from guinea pig peritoneal macrophages upon treatment with 10−5 M PAF for 60 min. Guinea pig peritoneal macrophages were treated with PAF for 8 hr and the conditioned medium was examined for cytokines. The medium exhibited cytocidal activity against mouse fibroblast L929 cells [tumor necrosis factor (TNF) activity], and this activity was comparable to that detected after treatment of cells with the bacterial lipopolysaccharide (LPS). Furthermore, the same conditioned medium also showed colony‐stimulating factor (CSF) activity. Generation of these cytokines was stereospecific. Our findings suggest that PAF is a unique macrophage activator that potentiates both respiratory burst/lysosomal enzyme release (early‐phase response) and monokine production/glucose consumption (late‐phase response).
Production of platelet‐activating factor by human normodense and hypodense eosinophils
Authors: Ojima‐Uchiyama Ayako , Masuzawa Yasuo , Sugiura Takayuki , Waku Keizo , Fukuda Takeshi , Makino Sohei 
Published: February 2007

AbstractNormodense eosinophils and neutrophils from normal donors produced considerable amounts of plateletactivating factor (PAF) when stimulated with ionophore A23187. PAF produced by eosinophils appeared to be degraded more rapidly than PAF formed by neutrophils, suggesting a higher activity of PAF‐degrading enzyme in eosinophils. Substantial proportions of PAF newly formed by both eosinophils and neutrophils were shown to be cell‐associated. By comparison, hypodense eosinophils obtained from a patient with idiopathic hypereosinophilic syndrome produced an extremely large amount of PAF and released much of it into the incubation medium. The accelerated formation of PAF in hypodense eosinophils may be related to various cardiovascular complications associated with hypereosinophilic syndrome.
Immunoregulatory functions of paf‐acether. VI. Dual effect on human B cell proliferation
Authors: Leprince Corinne , Vivier Eric , Treton Dominique , Galanaud Pierre , Benveniste Jacques , Richard Yolande , Thomas Yolene 
Published: February 2007

AbstractThe role of paf‐acether (paf), a phospholipid cytokine, in the modulation of human B cell function was investigated. Paf, from 1×10−5 M to 10−6 M, decreased B cell proliferation induced by both phorbol myristate acetate (PMA) and anti‐IgM antibodies (anti‐IgM Ab). By contrast, 1×10−7 M to 1×10−9 M paf enhanced PMA triggered, but not anti‐IgM triggered B cell proliferation. B cell proliferation was modulated between 24 and 72 hr of culture indicating that the effect of paf did not merely reflect a shift in proliferation kinetics. Interestingly, paf also enhanced the spontaneous proliferation of a Burkitt lymphoma‐derived B cell line, Raji, which suggests that paf can directly act on B cells. The modulatory effect of paf on peripheral blood B cells was independent of PMA concentration, yet the effect on Raji cells was dependent upon cell density. The data suggest that paf is a potent modulator of B cell function, and may be involved in the control of humoral immune response.
Calcium channel blockade inhibits platelet activating factor production by human umbilical vein endothelial cells
Authors: Tolins J. P. , Melemed A. , Sulciner D. , Gustafson K. S. , Vercellotti G. M. 
Published: February 2007

AbstractAn increase in intracellular calcium level is an important signal in the regulation of cellular responses under normal and pathological conditions. Because two key enzymes in the synthetic pathway of platelet activating factor (PAF), phospholipase A2 and acetyltransferase, are calcium dependent, we hypothesized that calcium channel blockade may inhibit agonist‐induced PAF synthesis. Primary cultures of human umbilical vein endothelial cells (EC), pre‐incubated with [3H]acetate, were exposed to thrombin (5 U/mL) and PAF production was quantitated by incorporation of radiolabel into the EC lipid fraction co‐migrating with exogenous PAF in thin‐layer chromatography. The effect of pre‐incubation with calcium channel blockers (verapamil, diltiazem, 10−4 M) or buffer was determined. Results (triplicate experiments,*P<0.05 vs buffer, † P<0.05 vs thrombin) demonstates that pre‐incubation with calcium channel blocker markedly inhibits thrombin‐induced PAF production (verapamil: buffer 273±122, thrombicin 10,735±1524*, thrombin+verapamil 178±91 † cpm/plate; diltiazem: buffer 1097±581, thrombin 15,283±2661*, thrombin+diltiazem 280±56 † cpm/plate). The effect of dialtiazem was dosedependent (% inhibition: 10−7 M, 46%; 10−5 M, 60%; 10−4 M, 98%). Diltiazem also inhibited bradykinin (10−8 M) induced PAF synthesis. In calcium‐free medium or in the presence of LaCl3 (10−3 M), the PAF response of EC to thrombin was blunted (buffer 582±360, thrombin 5394±1069, thrombin+calcium free medium 1055 ±571, thrombin+LaCl3 1271±58 cpm/plate). We conclude that calcium channel blockers present agonist‐induced PAF synthesis, possibly by preventing cellular calcium influx and activation of PAF synthetic enzymes. We speculate that this mechanism may underlie, at least in part, the beneficial effect of calcium channel blockade under various pathological conditions.
The effect of eicosapentaenoic acid consumption on human neutrophil chemiluminescence
Authors: Thompson Philip J. , Misso Neil L. A. , Passarelli Marion , Phillips Martin J. 
Published: February 2007

AbstractThe effect of eicosapentaenoic acid (EPA) on the inflammatory potential of neutrophils was investigated by supplementing the diets of 12 subjects with 2.16 g of EPA or 12 g of olive oil per day for 4 weeks in a double blind crossover study. Neutrophil function as assessed by luminol enhanced chemiluminescence responses to plateletactivating factor (PAF) and formyl‐methionyl‐leucyl‐EPA but not after olive oil consumption in the subjects who consumed EPA first. In contrast, EPA had no significant effect on neutrophil chemiluminescence in the subjects who consumed olive oil first. Dietary supplementation with EPA inhibits neutrophil responses to inflammatory mediators such as PAF while other fatty acids appear to modify the effects of EPA.
IgA immune aggregates stimulate platelet‐activating factor and superoxide anion production by human neutrophils. A comparison with IgG aggregates
Authors: Hernando Paloma , Egido Jesus , de Nicolas Rosario , Gonzalez Eva 
Published: February 2007

AbstractWe have examined the possibility that human polymorphonuclear cells exposed to IgA immune complexes can mediate the production of platelet‐activating factor (PAF) and oxygen radicals. We found that human IgA and IgG immune aggregates stimulated, to a similar extent, PAF and O2− production by human polymorphonuclear cells (PMN) in a concentration and time dependent manner. The PAF, that was largely associated with cells, was shown to be identical to synthetic PAF, as determined by physicochemical, chromatographic and enzymatic assay. Furthermore,de novo synthesis of PAF by PMN was shown to occur by incorporation of radioactive precursors, such as [3H]acetate. The addition of normal human serum to PMN incubated with IgG aggregates resulted in a significant amount of PAF formation which was not observed with IgA aggregates. By contrast, no change was seen in PMN O2− with either aggregates. The preincubation of PMN with cytochalasin B, an inhibitor of phagocytosis, did not affect PAF and O2− production by both aggregates. The results suggest that the interaction of PMN with the IgA complexes in blood vessel of lipid mediators, such as PAF and oxygen radicals that could contribute to the inflammatory response.
Calcium ion mobilization in neuronal cells induced by PAF
Authors: Kornecki Elizabeth , Ehrlich Yigal H. 
Published: February 2007

AbstractWe have reported previously that platelet‐activating factor (PAF) interacts with the neuronal cell line NG108‐15 (neuroblastoma X glioma hybrid) and the pheochromocytoma cell line, PC12. PAF acts on these cells by raising levels of intracellular free calcium ions. In the present report, we extend these studies. PAF induced the vesicular release of adenosine 5′‐triphosphate (ATP) from PC12 cells in a dose‐dependent manner. The PAF‐induced ATP release was inhibited by the PAF antagonists, CV‐3988 and CV‐6209, and the calcium antagonist prenylamine. The relevance of the interaction of PAF with neuronal cells was investigated further by using brain synaptosomal preparations and primary cortical and neostriatal cells. Nanomolar concentrations of PAF induced calcium transients in aequorin‐loaded synaptosomal preparations, and cortical and neostriatal cells were sensitive to the action of PAF. The possible physiological and pathophysiological roles of PAF in brain function are discussed.