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Y Denizot

Publications and source records attributed to Y Denizot.

121 records · Page 7Linked to original sources
PubMed1989

Biological and cellular responses to grass pollen in sensitive patients.

Using a noninvasive skin chamber technique, we studied the in vivo development of anaphylactic reactions in 8 pollen-sensitive patients suffering from seasonal allergic rhinitis/conjunctivitis/asthma and showing positive cutaneous reactions after intradermal allergen challenge. As agonists, histamine and pollen were introduced into the skin chambers and left in contact with superficial dermis during 6 h. The release of mediators (histamine and prostaglandin [PG] D2) and the modifications in protein diffusion occurring during the immediate (30 min) and the late (6 and 24 h) cutaneous reaction phases were quantitatively analyzed. 24 h after agonist introduction, the recruitment of inflammatory cells on the superficial dermis was studied by use of Rebuck's windows. Histamine release in pollen-containing skin chambers was immediate and persisted until the 24th h despite replacement of the agonists by control medium at the 6th h. An intense PGD2 release occurred as soon as the first 30 min in chambers containing either exogenous histamine or pollen and was maintained until the 24th h. Protein diffusion induced by histamine and pollen was similar to the control one at 30 min but was intensely enhanced at the 6th h. At the 24th h, pollen-induced protein diffusion was still intense whereas that induced by histamine was analogous to the control one. 24 h after pollen challenge, numerous eosinophils were recruited on the superficial dermis but almost none were observed after control medium or histamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Eosinophils↗
PubMed1989

[Contamination of fermented milk products by proinflammatory autacoid paf-acether].

Paf-acether (platelet-activating factor) is one of the most potent inflammatory mediators synthesized by and acting on most inflammatory cells. It also displays potent immunoregulatory properties. Two metabolic steps are involved in its biosynthesis: the action of a phospholipase A2 on membrane alkyl-acyl (long chain) phospholipids with choline polar head results in the production of lyso paf-acether, and acetylation of the lyso compound by an acetyltransferase yields the biologically active molecule. Recently we showed that E. coli and other bacteria are able to produce paf-acether using exogenous lyso paf-acether. This finding prompted us to search for the presence of paf-acether in fermented milk products. The fraction corresponding to paf-acether isolated from milk exhibited the same physicochemical and biological characteristics as synthetic paf-acether and that from eukaryotic cells. The presence of a biologically active phospholipid in fermented products may bring new perspectives with respect to the study of gastrointestinal diseases as well as the putative immunostimulating effect of yogurt.

Dairy Products↗
PubMed1988

Biosynthesis of paf-acether factor-acether by human skin fibroblasts in vitro.

The synthesis and release of paf-acether by fibroblasts from normal human skin was investigated in vitro. When fibroblasts in suspension (1 X 10(6) cells) were stimulated with 2 microM Ca1+ ionophore A23187 (Io), they synthesized a material that aggregated aspirin-treated washed rabbit platelets and was identified as paf because 1) the platelet aggregation it induced was inhibited by BN 52021, an antagonist of paf putative receptors; 2) the factor was inactivated by phospholipase A2 but was insensitive to lipase from Rhizopus arrhizus; 3) it exhibited the same retention time as synthetic paf during standard and reverse phase HPLC elution. Paf production by fibroblasts occurred as soon as the first min of Io stimulation (287 +/- 92 pg/1 X 10(6) cells), reached a maximum at 5 min (369 +/- 85 pg/1 X 10(6) cells) and decreased thereafter. Half of the fibroblast-produced paf was recovered in supernatants. Addition of exogenous 1-O-alkyl-sn-glycero-3-phosphocholine (lyso-paf) at 0.1 microM and/or acetyl-coenzyme A at 0.1 mM to fibroblasts during Io stimulation enhanced paf production by two- and three-fold, respectively. The paf precursors, i.e., 1-O-alkyl-2-acyl-sn-glycero-3-phosphocholine (1-alkyl-2-acyl-GPC) and lyso-paf, were detected in fibroblasts either stimulated with Io or not. These precursors exhibited 80% hexadecyl and 20% octadecyl chains at the sn-1 position of the molecules, as determined by reverse phase HPLC and gas chromatography analysis. The present results are the first to demonstrate the synthesis and release of paf by fibroblasts from normal human skin. Such production within the dermis might account for the development of cutaneous inflammation and for the pathogenesis of many skin disorders.

Adult↗
PubMed1986

[Synthesis of paf-acether by E. coli K12].

Paf-acether (platelet-activating factor) is one of the most potent mediator of inflammation released from and acting on most cells that participate in inflammatory diseases. Its molecular structure is 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine. Two metabolic steps are involved in its biosynthesis: the action of a phospholipase A2 on choline-containing membrane alkyl-ether lipids results in the production of lyso paf-acether and acetylation of the lyso compound by an acetyltransferase yields the biologically active molecule. Membrane alkyl-ether lipids can therefore be considered as potential precursors of paf-acether and their composition has been studied in various cell types. In this work, we investigated the presence of paf-acether in E. coli. Our results showed that paf-acether can be obtained from E. coli K12 under a variety of bacterial growth conditions. Paf-acether from E. coli exhibited the same physicochemical and biological characteristics as synthetic paf-acether and that from eucaryotic cells. Therefore, it appears that E. coli itself has the ability of producing paf-acether, a result that could be of some importance with respect to the pathogenesis of Enterobacteria and the use of E. coli in the recombinant DNA technology.

Animals↗
PubMedDate not supplied

Modulation of gut wall paf-acether and precursors by intestinal microflora.

Comparison between holoxenic and axenic mice led to the conclusion that the presence of an intestinal microflora produced a decrease in wall paf in conventional mouse caecum, whereas an increase in wall lyso-paf and alkyl-acyl-glycerophosphocholine (A-A-GPC) content was noticed. By contrast, the presence of flora had no significant incidence on wall paf, lyso-paf and A-A-GPC content of conventional mouse jejunum. Thus, the modulation of gut wall phospholipid composition by intestinal microflora is evidenced for the first time.

Animals↗
PubMedDate not supplied

Is there a role of platelet-activating factor in human lung cancer?

Platelet-activating factor (PAF) is a lipid mediator that stimulates the in vitro growth of various human tumour cell lines and that enhances the effect of vascular endothelial growth factor that plays a key role during angiogenesis of human cancer. In this study, we assessed the levels of PAF and of the acetylhydrolase activity (AHA, the PAF degrading enzyme) in patients with lung cancer. Results indicated no significant differences between blood PAF amounts of lung cancer patients (91+/-33 pg/ml, n=31) and a control group of patients with chronic obstructive pulmonary disease (COPD) induced by habitual smoking (117+/-28 pg/ml, n=10). Similarly, their serum AHA levels were not different (67.9+/-3.0 nmol/min/ml as compared to 68.3+/-5.2 nmol/min/ml for lung cancer patients and controls, respectively). In contrast, PAF amounts were markedly (P=0.01, t-test for paired data) reduced in the lung tumour tissues (77+/-29 pg/g, n=10) as compared to the non-tumour tissues (208+/-67 pg/g, n=10). These low levels of PAF were not related to a lower amounts of the lyso-PAF precursor but to an elevated (P=0.01, t-test for paired data) AHA in the tumour tissues (37.0+/-4.9 nmol/min/g, n=10) as compared to the non-tumour tissues (24.6+/-2.6 nmol/min/ml, n=10). Reverse transcriptase polymerase chain reaction experiments showed the presence of the PAF receptor (PAF-R) transcript 1 but not transcript 2 in blood mononuclear cells of lung cancer patients and COPD patients. Flow cytometry experiments did not highlight differences in the number and the distribution of PAF-R on their circulating leukocytes. In conclusion, this clinical study highlights no evidence for a potential important role of PAF during human lung cancer.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMedDate not supplied

Elevated levels of paf-acether in blood of patients with type 1 diabetes mellitus.

Infusion of paf-acether (paf, first described as platelet-activating factor) into animals stimulates glycogenolysis and lipolysis and decreases insulin levels. This study reports a 50-fold increase in blood levels of paf in patients with Type 1 insulin-dependent diabetes mellitus without micro or macrovascular complications (1.07 +/- 0.42 ng/ml, n = 10) as compared with healthy volunteers (0.04 +/- 0.02 ng/ml, n = 9). By contrast, paf is not statistically elevated (p greater than 0.05) in patients with Type 2 non-insulin-dependent, diabetes mellitus with lipid abnormalities and micro or macrovascular complications (0.32 +/- 0.18 ng/ml, n = 9). In the three groups same levels of paf precursors and acetylhydrolase activity (the enzyme which inactivates paf) were noted suggesting an increase in paf biosynthesis by Type 1 diabetic patients. Elevated paf levels could perpetuate hyperglycaemia and tend to promote or accentuate micro or macrovascular complications. This study adds another biological difference between Type 1 and Type 2 diabetes.

Adult↗
PubMedDate not supplied

Pulmonary edema and shock after high-dose aracytine-C for lymphoma; possible role of TNF-alpha and PAF.

Four out of 23 consecutive patients treated with high-dose Ara-C for lymphomas in our institution developed a strikingly similar syndrome during the perfusion. It was characterized by the onset of fever, diarrhea, shock, pulmonary edema, acute renal failure, metabolic acidosis, weight gain and leukocytosis. Thorough bacteriological screening failed to provide evidence of infection. Sequential biological assays of IL-1, IL-2, TNF and PAF were performed during Ara-C infusion to ten patients, including the four who developed the syndrome. TNF and PAF activity was found in the serum of respectively two and four of the cases, but not in the six controls. As TNF and PAF are thought to be involved in the development of septic shock and adult respiratory distress syndrome, we hypothesize that high-dose Ara-C may be associated with cytokine release.

Acute Kidney Injury↗
PubMedDate not supplied

Platelet-activating factor and haematopoiesis. XI. Platelet-activating factor has no effect on the production of interleukin-6 and tumor necrosis factor-alpha by human bone marrow stromal cells.

PAF is a phospholipid mediator of inflammation with stimulates IL-6 production by murine skin fibroblasts. Although PAF is present in human bone marrow, its role in haematopoiesis is unknown. We have assessed whether PAF stimulates IL-6 and TNF-alpha production by human bone marrow stromal cells (mostly fibroblast-like cells). We report that PAF (1 nM to 10 microM) has no effect on the synthesis of IL-6 and TNF-alpha by human bone marrow stromal cells. This difference may be due to the widely accepted concept "tissue-specific fibroblasts". The role of PAF in the regulation of human haematopoiesis remains to be elucidated.

Bone Marrow↗