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Biomedical subjects

J Maclouf

Publications and source records attributed to J Maclouf.

At least 145 records · Page 8Linked to original sources
PubMed1987

Absence of plasma prostacyclin stimulating activity deficiency in hemolytic uremic syndrome.

We compared the effect of plasma from 19 children with hemolytic uremic syndrome (HUS) on prostacyclin (PGI2) production by fresh rat aortic rings to the effect of plasma from 17 age- and sex-matched normal children, taking into account the PGI2 baseline aortic production (PGI2 release in presence of buffer, 21 determinations). After 10, 20, 30, 40, and 60 minutes incubation of rat aortic tissue with either plasma or buffer, the presence of PGI2 was studied by measuring by radioimmunoassay (RIA) the concentration of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha). 6-keto-PGF1 alpha production increased with time in the two groups of plasma samples and in the presence of buffer, but 6-keto-PGF1 alpha production (ng/mg dried tissue) after 30 minutes incubation and mean 6-keto-PGF1 alpha production (slope of regression line, ng/mg/min) were significantly (P less than 0.01) lower in the presence of normal plasma compared with buffer, and significantly (P less than 0.01) higher in the presence of HUS plasma compared with normal plasma. There was no significant difference between buffer and HUS plasma. We conclude that, under our experimental conditions, normal plasma had an inhibitory activity on 6-keto-PGF1 alpha production by rat aorta. This inhibitory activity was absent in HUS plasma.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Abnormal phosphoinositide metabolism and protein phosphorylation in platelets from a patient with the grey platelet syndrome.

Washed platelets isolated from one patient suffering from the inherited grey platelet syndrome were studied during thrombin-induced activation. The agonist-induced changes in (i) morphology, (ii) typical functional cell responses, (iii) membrane phospholipid metabolism and protein phosphorylation were studied and compared with the changes obtained with normal platelets. The morphology of the platelets as visualized by electron microscopy confirmed the almost total absence of intracellular alpha-granules and marked vacuolization. During thrombin stimulation the morphological changes were clearly delayed as compared to normal platelets, the granule centralization and aggregation occurred only 15 s after thrombin addition instead of 5 s in normal platelets. After 15 s, however, even though no alpha-granules were observed, a ring-like structure occurred centrally, indicating that they are not a prerequisite for this reaction. The whole release reaction, i.e. liberation of [14C]serotonin from dense granules and beta-N-acetylglucosaminidase activity from lysosomes, and the thromboxane synthesis were delayed and remained lower than in normal platelets. No thrombin-induced phosphatidyl 4,5-bisphosphate breakdown was measurable on 32P-prelabelled platelets although [32P]phosphatidate formation occurred normally. Phosphorylation time courses of myosin light chain (P20) and of protein P43 (mol wt 43,000) markedly differed from those of controls, being less than half of the normal during the first 15 s and remaining subnormal even after complete aggregation. These results suggest that in platelets devoid of alpha-granules a deficient transmembrane signalling system is likely responsible for the impaired physiological responses.

Blood Platelet Disorders↗
PubMed1987

[Ex vivo study of blood platelet activation in healthy subjects or coronary disease patients after oral intake of molsidomine].

Platelet activation (aggregation, serotonin release, TXB2 synthesis) was studied in 8 normal subjects and 5 patients with unstable angina before and after molsidomine treatment. Serotonin release was the most altered parameter after molsidomine treatment in the group of normal subjects. No significant effect could be detected in patients since platelet reactivity varied in a wide range.

Administration, Oral↗
PubMed1986

Stereospecific induction of starfish oocyte maturation by (8R)-hydroxyeicosatetraenoic acid.

Oocyte maturation (meiosis reinitiation) in starfish is induced by the natural hormone 1-methyladenine. This induction of meiotic divisions can be triggered also by four fatty acids: 5,8,11-20:3; 5,8,11,14-20:4 (arachidonic acid); 6,9,12,15-20:4; 5,8,11,14,17-20:5, all other fatty acids being completely inactive. This maturation triggered by eicosanoids occurs in the micromolar range and is facilitated by the presence of calcium. A variety of arachidonic acid derivatives (esters, epoxides, etc.) and metabolites (cyclooxygenase and lipoxygenase products) has been tested; the biological activity is restricted to 8-hydroxyeicosatetraenoic acid (8-HETE), other mono- and poly-HETEs being completely inactive. Maturation triggered by 8-HETE occurs around 10 nM and is insensitive to the presence of calcium. 8-HETE methyl ester and 8-hydroperoxyeicosatetraenoic acid are able to induce maturation at higher concentrations. Both (8S) and (8R) stereoisomers have been tested; the biological activity is strictly restricted to the (8R) isomer. 8-HETE triggers a complete maturation, i.e. maturation-promoting factor appearance, germinal vesicle breakdown, emission of the polar bodies, and formation of a female pronucleus. (8R)-HETE, but not (8S)-HETE, triggers the typical decrease in cyclic AMP concentration induced by 1-methyladenine and the burst of protein phosphorylation associated with maturation. Starfish oocytes oxidize exogenous arachidonic acid into 8-HETE and other HETEs. 8-HETE was identified, after high pressure liquid chromatography purification, by gas chromatography mass spectrometry. Furthermore, it was found that the starfish oocytes only produce the (8R)-HETE isomer. This highly stereospecific induction of oocyte maturation by (8R)-HETE suggests that this fatty acid, or a very closely related fatty acid, may play a role in the transduction of the 1-methyladenine message at the plasma membrane level.

Animals↗
PubMed1986

Inhibitory effects of a novel platelet activating factor (PAF) antagonist (BN 52021) on antigen-induced prostaglandin and thromboxane formation by the guinea pig lung.

The effects of a new Platelet-Activating Factor (PAF-acether) antagonist (BN 52021) extracted from Ginkgo biloba leaves have been studied on the release of metabolites of arachidonic acid in IgG-dependent guinea pig pulmonary anaphylaxis in vitro. Prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) were assayed using a novel ELISA technique. The release of PGE2 and TxB2 from anaphylactic lungs reached a maximum 4-5 min following the antigen challenge (about 3.2 and 31.0 ng/ml respectively) and decayed slowly during the following 25 min. BN 52021 (1, 3 and 30 micrograms/ml) produced dose-dependent decreases of the release of PGE2 and TxB2. These results suggest that there are some interactions between the release of icosanoids and PAF-acether in anaphylaxis.

Anaphylaxis↗
PubMed1986

Analysis of 6-keto PGF1 alpha, 5-HETE, and LTC4 in rat lung: comparison of GM/MS, RIA, and EIA.

The recent availability of fast and sensitive radioimmunoassay (RIA) and enzyme immunoassay (EIA) procedures to measure icosanoids has led to utilization of these techniques by many investigators. A major concern has been that techniques based on immunoreactivity may lack specificity, in particular if complex biologic fluids or tissue extracts are evaluated. The purpose of this investigation was the comparison of icosanoid measurements obtained either with EIA or RIA with those obtained by gas chromatography/mass spectrometry (GC/MS). Rats were injected with Salmonella enteritidis endotoxin, killed at various times after the injection and the lung extract assayed for 6-keto-PGF1 alpha, 5-HETE and LTC4. By EIA lung tissue was found to contain large quantities of 6-keto-PGF1 alpha after endotoxin stimulation. Comparisons made between EIA and GC/MS analysis showed good correlation between 6-keto-PGF1 alpha amounts in lung as determined by each technique. It was also determined that little purification of lung extract was needed to obtain reliable quantitation of 6-keto-PGF1 alpha, probably due to the specificity of the antibody and the large quantity of this prostaglandin produced. Crudely purified (Sep-Pak) lung extracts gave 5-HETE levels by RIA which were highly correlated with GC/MS values, but RIA values were 70% higher than those obtained by GC/MS. The presence of other components in lung extract which cross react with this 5-HETE antibody was probably responsible for the higher values obtained by RIA. LTC4 was measured by immunoassay in crude lung extracts, as well as after Sep-Pak purification and HPLC purification. LTC4 levels were identical in unpurified lung extract and after Sep-Pak purification, but decreased substantially after HPLC purification. Thus, by validating the icosanoid immunoassays, we have found that they can give accurate and reproducible results in lung tissue, although LTC4 and 5-HETE must be purified prior to analysis.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Development of a radioimmunoassay for prostaglandin D2 using an antiserum against 11-methoxime prostaglandin D2.

A sensitive and specific radioimmunoassay for prostaglandin D2 has been developed using its stabilized 11-methoxime derivative, which was obtained after treatment of prostaglandin D2 with methoxamine-HCl. The antiserum was obtained after injection of prostaglandin D2-methoxamine coupled to bovine serum albumin. A (125I)-Histamide prostaglandin D2-methoxamine tracer was prepared by iodination of the corresponding histamide, followed by thin layer chromatography purification. The sensitivity of the assay was 280 femtomoles per ml at 50% displacement. The cross reactivities were 15% with prostaglandin D1-methoxamine and less than 0.20% with other prostaglandins. Determination of the half-life of prostaglandin D2 in a solution containing albumin was also carried out, since it has been shown to catalyze prostaglandin D2 destruction. The unstability of this prostaglandin is due to the presence of a beta-hydroxy ketone group, and all prostaglandins possessing this labile moiety could be stabilized by such a derivatization before developing a radioimmunoassay.

Chromatography, Thin Layer↗
PubMed1986

Potentiation of 5-lipoxygenase metabolism by human neutrophils using a combination of activators.

Platelet-derived 12-hydroperoxy-5,8,10,14-icosatetraenoic acid (12-HPETE) cannot increase the synthesis of leukotriene B4 metabolites by human neutrophils activated by 1-0-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (Paf Acether) at 10(-9) and 10(-8) M in contrast to 1 microM arachidonic acid. The combination of the 3 inducers at various concentrations resulted in a potentiation of the formation of leukotriene B4 metabolites suggesting that multiregulatory steps play a key role to govern the 5-lipoxygenase activity. These results suggest that the use of agents that can act synergistically to produce leukotrienes may be worthwhile investigating to understand some aspects of the leukotriene biosynthesis.

Arachidonate 5-Lipoxygenase↗
PubMed1986

Contrasting effects of fatty acids on oocyte maturation in several starfish species.

Oocyte maturation (meiosis reinitiation) in starfish is induced by the natural hormone 1-methyladenine. In some species (group 2) oocyte maturation can be induced by micromolar concentrations of a few fatty acids such as arachidonic and eicosapentaenoic acids or by nanomolar concentrations of hydroxyeicosatetraenoic acid. Complete maturation is triggered: increased protein phosphorylation, appearance of the cytoplasmic "maturation-promoting factor", germinal vesicle breakdown, emission of the two polar bodies and formation of the female pronucleus. In other species (group 1), however, no maturation can be induced by the fatty acids active in the species of group 2, despite a large variety of experimental conditions.

Adenine↗
PubMed1986

Thrombocytopenia with thrombocytopathy possibly related to abnormalities of intracellular Ca++ fluxes and followed by the development of leukaemia.

A patient is described who presented a thrombocytopenia with thrombocytopathy followed by the development of a leukaemia. The disorder was characterized by decreased aggregation in the presence of ADP, and a lack of aggregation in the presence of arachidonic acid, natural endoperoxide or collagen. In parallel, 14C-serotonin release was severely decreased or nil in response to these inducers. Thrombin induced a slightly decreased aggregation and a normal 14C-serotonin release. Thromboxane B2 (T X B2) synthesis was normal after stimulation by arachidonic acid, natural endoperoxide or thrombin showing a normal arachidonate metabolism. In addition, the mepacrine test showed no significant decrease of the number of dense bodies with an average of 4.6 per platelet (versus 5.4 +/- 0.8 sd in controls). Stimulation by ionophore A 23187 failed to induce aggregation, 14C-serotonin release, or T X B2 synthesis. Furthermore, in the presence of EDTA, A 23187 did not provoke activation as reflected by 14C-serotonin release or T X B2 synthesis. Thus, in this case of thrombocytopathy, the hypothesis of abnormal intracellular Ca++ fluxes responsible for the defective platelet release phenomenon, was suggested.

Adenosine Diphosphate↗
PubMed1986

Prolonged remission in Raynaud's phenomenon after prostacyclin infusion.

We infused prostacyclin (PGI2) (7.5 ng/kg/min) during 5 h, three times at weekly intervals in 8 patients with Raynaud's phenomenon (RP). In 4 patients, improvement was long-term, more than 90 days after the last infusion (good responders); in 3 patients, improvement was mild, less than 15 days, and in one patient no improvement was observed (poor responders). Clinical response was always accompanied by improvement, although less prolonged, of capillary appearance and/or function, as judged by microscopy and/or hemodynamic tests (pulse volume index; radial artery blood flow). Lastly, increased catabolism of PGI2 seemed to be excluded in poor responders, since no statistical difference in PGI2 metabolism could be observed between the two groups.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Release of prostacyclin after erythrocyte adhesion to cultured vascular endothelium.

Endothelial cell damage is considered to be the initial step in the genesis of thrombosis and atherosclerosis. Recently, the adhesion of erythrocytes from patients with diabetes or sickle cell anemia to endothelial cells was found to be increased and correlated with the severity of vascular complications. We have measured by radioimmunoassay the release of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) as an index of prostacyclin (PGI2) production, during red cell adhesion to endothelial cells in culture. The amount of 6-keto-PGF1 alpha released after incubation with normal red cells was similar to that observed with buffer (1.07 +/- 0.32 nmol/10(6) endothelial cells). However, after the adhesion of erythrocytes from patients with diabetes or sickle cell anemia, the amount of 6-keto-PGF1 alpha produced was significantly increased (P less than 0.01) and was correlated with the extent of erythrocyte adhesion (P less than 0.05). Tritium-labeled PGI2 was found to bind to erythrocytes, and the binding was time and concentration dependent. PGI2 release was inhibited by the cyclooxygenase inhibitor (flurbiprofen), whereas red cell adhesion remained unchanged. Fibrinogen potentiated erythrocyte adhesion and PGI2 production. The increase in PGI2 production after the adhesion of red cells from patients with diabetes or sickle cell anemia to endothelial cells indicates that endothelium may be damaged by abnormal erythrocyte adhesion.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

[Role of prostaglandins and thromboxanes in cardiovascular physiopathology].

Prostaglandins and thromboxanes originate from lipid metabolism. Their precise role remains obscure despite our better understanding of their potent pharmacological properties reflected in their potent biological activities. Prostaglandins are most probably involved in various cardiovascular diseases, although few satisfactory methods are available to evaluate such a role in vivo. The fact that most antithrombotic drugs interfere with the arachidonic acid cascade provides a rationale to their mode of action and their use. The development of drugs acting more selectively on arachidonic acid metabolism should constitute a therapeutic improvement in cardiovascular diseases.

Arachidonic Acids↗
PubMed1985

Interference of some flavonoids and non-steroidal anti-inflammatory drugs with oxidative metabolism of arachidonic acid by human platelets and neutrophils.

The effect of ten flavonoids was studied on the stimulation of washed human platelets by either arachidonic acid or thrombin. The oxygenated metabolites released were analyzed by radioimmunoassay, glass-capillary-column gas chromatography and high-pressure liquid chromatography. No effect was evidenced for naringenin, rutinose and phloridzin up to 1000 microM. Thromboxane B2 and 12-hydroxyeicosatetraenoic acid production was depressed simultaneously by all other compounds at different IC50. When tested for their effect on reversibility, however, cyclooxygenase and lipoxygenase inhibition was found to be different depending upon the flavonoid used. All compounds, except morin and rutin, inhibited platelet aggregation and [14C]serotonin release with parallel inhibition of thromboxane synthesis when tested on arachidonic acid-induced platelet-rich plasma stimulation. Some flavonoids inhibited the metabolism of human neutrophils stimulated by ionophore A23187 as assessed by high-performance liquid chromatography. Our results show that flavonoids interfere with the different oxidative metabolisms of arachidonic acid. No clearcut specificity could be found between one compound and one metabolic pathway.

Anti-Inflammatory Agents↗
PubMed1985

Change in the physical state of platelet plasma membranes upon ionophore A23187 activation. A fluorescence polarization study.

Human platelets were isolated and fluorescence-labelled by 1,6-diphenylhexatriene. Diphenylhexatriene was essentially localized in the plasma membrane, as indicated by trinitrobenzenesulfonate-quenching experiments. A decrease of the fluorescence polarization of diphenylhexatriene was observed upon ionophore A23187 addition in the absence of aggregation. 0.3 microM ionophore allowed to reach the maximum rate of the decrease of fluorescence polarization; it also maximally stimulated the light transmission change, the serotonin release and the thromboxane B2 synthesis. The amplitude of the fluorescence polarization decrease was maximum at platelet concentrations between 4 X 10(7) and 7 X 10(7)/ml. The presence of Ca2+ in the medium increased the rate constant of the polarization change. Chlorpromazine (60 microM) completely inhibited this transition, but at 30 microM its inhibitory effect was reversed by Ca2+. The membrane events implied in platelet activation very likely lead to fluidization of the plasma membrane, perhaps by its fusion with the membranes of internal granules which are relatively depleted of cholesterol. Ca2+ plays a central role in the triggering of the observed effects at the membrane level.

Blood Platelets↗