PAF and Haematopoiesis. I. 5-Fluoro-Uracil Induces PAF Production in Haematopoietic Organs of Rats

Haematopoietic organs of rats were examined for the presence of platelet-activating factor (PAF) and acetylhydrolase before and after treatment with 5-fluoro-uracil (5-FU) (200 mg/kg) a chemotherapeutic compound with apoptotic effects. PAF was reported in thymus, spleen and femoral bone marrow of rats with or without 5-FU. Although acetylhydrolase activity in organs was not affected by 5-FU treatment, elevated levels of PAF were observed in thymus and spleen. For the first time PAF is reported in haematopoietic organs of rats, strengthening in vitro data suggesting its role in the apoptotic processes in thymus, in the modulation of the immune response, and in the regulation of haematopoiesis

Decreased levels of serum platelet-activating factor acetylhydrolase in patients with rheumatic diseases

PAF is a potent inflammatory compound known to stimulate the release of various cytokines involved in rheumatic diseases. Elevated blood PAF levels are reported in these patients. We report that serum PAF acetylhydrolase activity (AHA) levels are decreased in patients with rheumatoid arthritis or osteoarthritis as compared to healthy controls. Serum and synovial fluid AHA levels were correlated in these patients. The present study suggests the potential role of AHA in controling systemic and/or local PAF levels in patients with rheumatic diseases

Incorporation and effect of arachidonic acid on the growth of human myeloma cell lines.

The objectives of this work are to investigate the incorporation of arachidonic acid (AA) in the human myeloma cell lines OPM2, U266 and IM9, and to assess the effect of AA and lipoxygenase products of AA on their growth. The kinetics of acylation of [3H]AA indicates that myeloma cells incorporate AA into their membrane phospholipids and triglycerides. PLA2-treatment and base hydrolysis experiments confirm that [3H]AA is incorporated unmodified in U266, IM9 and OPM2 phospholipids, and is linked by an ester bond. Prelabeling-chase experiments indicate no trafficking of labeled AA among the various phospholipid species. Addition of AA and lipoxygenase products of AA (leukotriene B4 and C4, lipoxin A4 and B4, 12- and 15-hydroxyeicosatetraenoic acid) have no effect on U266, IM9 and OPM2 proliferation assessed by [3H]thymidine incorporation into DNA. In conclusion, while human myeloma cells readily incorporate AA in their membrane phospholipids and triglycerides, AA and lipoxygenase products are not important modulators of their proliferation

Aspects de la réception des classiques dans la Renaissance italienne : le monologue lyrique et la narration épique

Un cas fascinant de la reprise du monde classique dans la culture italienne est celui de Pétrarque. Le grand écrivain toscan donna vie à un idéal de renaissance du monde antique qui inaugura l’humanisme : le retour à une langue latine purifiée des sédiments du latin médiéval, la possibilité d’aborder de nouveaux genres se rattachant directement à ceux qui existaient dans l’Antiquité, l’idée même d’une autobiographie idéale, rythmée par une activité épistolaire en latin qui devait promouvoir le rôle nouveau que l’intellectuel européen allait jouer au XVe siècle. Cependant, l’activité littéraire de Pétrarque recèle des aspects moins évidents. Sa production en langue vulgaire surtout, de dimension très réduite par rapport à celle en latin, se concentre sur les thèmes romans de la lyrique amoureuse, dans laquelle le sujet est doté d’une tension tragique tout à fait étrangère à la tradition classique et où la reprise de structures latines dans l’organisation syntaxique elle-même crée des effets d’ambiguïté extraordinaires, signes de l’inquiétude du désir du sujet. Un second aspect est en lien avec le récit chevaleresque du XVe siècle, un genre très éloigné de la tradition épique latine sur le plan des thèmes et de l’intrigue. Toutefois, les auteurs de poèmes chevaleresques italiens, et parmi eux surtout Matteo Maria Boiardo, récupèrent une figure de style caractéristique de l’épopée antique, de l’Enéide, par exemple, ou de la Thébaïde : l’allitération. Les structures allitératives sont employées, comme dans la littérature latine, pour accentuer la tension produite par le récit, pour créer des effets acoustiques qui puissent accompagner la force évocatrice des images, leur impression dans la mémoire

Arachidonic acid and freshly isolated human bone marrow mononuclear cells.

Arachidonic acid (AA), a fatty acid found in the human bone marrow plasma, is the precursor of eicosanoids that modulate bone marrow haematopoiesis. To further our understanding of the role of AA in the bone marrow physiology, we have assessed its incorporation in human bone marrow mononuclear cells. Gas chromatography analysis indicates the presence of AA in their fatty acid composition. In bone marrow mononuclear cells, [3H]-AA is incorporated into triglycerides and is later delivered into phospholipids, a result not observed with blood mononuclear cells. Prelabelling-chase experiments indicate a trafficking of labelled AA from phosphatidylcholine to phosphatidylethanolamine. Stimulation of prelabelled bone marrow mononuclear cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) results in the release of a part of the incorporated labelled AA. Finally, exogenous AA (up to 1 microM) has no significant effect on cell growth. In conclusion, human bone marrow mononuclear cells participate to the control of marrow AA concentrations by incorporating AA into phospholipids and triglycerides. In turn, bone marrow mononuclear cells can release AA in response to the potent haematopoietic growth factor GM-CSF

PAF and haematopoiesis: III. Presence and metabolism of platelet-activating factor in human bone marrow

AbstractPlatelet-activating factor (PAF) is a phospholipid compound with major immunoregulatory activities. The present study shows that human bone marrow contains 576 ± 39 pg PAF/ml (n = 35). Bone marrow-derived PAF exhibits the same biophysical and biological properties that synthetic PAF. PAF concentrations in bone marrow are correlated with the granulocyte (r = 0.4, P = 0.02) but not with the lymphocyte (r = 0.24, P = 0.17) and the monocyte (r = 0.12, P = 0.48) counts. In bone marrow PAF is inactivated by a plasma PAF acetylhydrolase activity (48.0 ± 2.3 nmol/min per ml, n = 34). Experiments with [3H]PAF indicate that human bone marrow cells actively metabolize this potent molecule by the deacetylation-transacylation pathway. Results of this investigation indicate the permanent presence of significant amounts of PAF in bone marrow suggesting its putative involvement in the processes of bone marrow cell proliferation and maturation

Tumour necrosis factor-alpha (TNFα) stimulates the growth of human bone marrow stromal cells

This study reports that TNF-α is a potent mitogen for human bone marrow sternal cells in vitro (assessed by [3H]-thymidine incorporation into DNA and cell counts). In contrast, cytokines such as IL-1α, IL-1β, IL-2, IL-3, IL-4, IL-6, LIF, SCF, M-CSF, G-CSF and GM-CSF had no effect. The effect of TNF-α on the growth of human bone marrow stromal cells could be of importance during inflammatory processes which take place in the marrow, for example marrow fibrosis