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The performance of the energy dispersive spectrometer (EDS) detectors has to be established in its original state and monitored periodically to ensure the stability and long-term performance of the system. Because EDS detectors are cooled by liquid nitrogen and because the environment is not an ultra-high vacuum, ice and contaminants will buld up in front of the detector crystal, decreasing the detection efficiency at low energy. Few performance tests are suitable for the specifics problems found at low energy. The proposed test is based on a new procedure for the modelling of the decrease of detection efficiency (DODE) with time (Hovington et al. 1993). It was found that the deposition rate of both ice and carbon increased significantly when porous uncoated samples were observed. Significant difference between spectra acquired immediately after different conditioning was also found. The proposed procedure can be used to determine the optimum time before a conditioning cycle, to detect an abnormal accumulation of contaminant both in front of the detector and at the sample surface, and to diagnose a broken window and a malfunction in the conditioning apparatus.

The adherence ability of cement clinker on magnesia–spinel refractories is investigated, using a sandwich test, at 1550°C for 30 min under a load of 5.3 kPa. Fractional factorial experiments determine that the silica ratio (SR)—SiO2/(Al2O3+Fe2O3) and particle size of raw meal, as well as heating rate, have a significant effect on adherence ability. Microstructural analyses indicate that the adherence ability depends upon reactions between clinker and refractories at high temperature. Only spinel reacts with CaO and 3CaO·SiO2 from clinker to form n-calcium aluminate (such as 3CaO·Al2O3, 12CaO·7Al2O3, CaO·Al2O3), but there is no reaction between MgO and the clinker. Fine crystalline spinel, evenly distributed in magnesia-based brick, is prone to reacting with lime-containing phases from clinker to form low melting phases and a belite-enriched zone at the clinker/brick interface. This reaction positively contributes to the high adherence on a magnesia−spinel brick. The high content of liquid in clinker with low SR accelerates reactions between spinel and clinker, while a limited reaction occurs at the brick/clinker interface with high silica.

Activating mutations of the calcium-sensing receptor (CaR) can cause isolated hypoparathyroidism. Treatment of hypocalcemia in these patients remains to be optimized, because the use of 1-hydroxylated vitamin D3 derivatives can cause hypercalciuria and nephrocalcinosis. We identified activating CaR mutations in 8 (42%) of 19 unrelated probands with isolated hypoparathyroidism. The severity of hypocalcemic symptoms at diagnosis was independent of age, mutation type, or mode of inheritance but was related to the degree of hypocalcemia; serum Ca was 1.97 +/- 0.08, 1.82 +/- 0.14, and 1.54 +/- 0.22 mmol/liter, respectively, in asymptomatic (n = 7), mildly symptomatic (n = 8), and severely symptomatic patients (n = 6). Hypocalcemia segregated with the CaR mutation, but no phenotype-genotype relationships were identified. Fourteen patients received regular 1-hydroxylated vitamin D3 treatment (mean duration, 7.2 +/- 4.9 yr). Nine had hypercalciuric episodes, which were associated with nephrocalcinosis in eight cases. Serum Ca during treatment predicted hypercalciuria and nephrocalcinosis poorly, because either or both of the latter could develop in hypocalcemic patients. Thus, mutational analysis of the CaR gene should be considered early in the work-up of isolated hypoparathyroidism. Treatment options should be weighed carefully in patients with serum Ca below 1.95 mmol/liter. The risk of nephrocalcinosis during treatment can be minimized by carefully monitoring urinary Ca excretion.

The paper deals with the elastic behavior of MgO/C refractories used in BOF at temperatures up to 1400°C in air or inert atmosphere. Measurements have been made by the way of a high temperature ultrasonic technique. Heating-cooling cycles and long time aging in the range 700–1400°C show strong variations of Young’s modulus which have been interpreted with the aid of XRD analysis, SEM observations and EDS analysis. Carbon oxidation and sintering of MgO particles are found to be responsible of the major parts of the measured evolutions. ©

The present investigation describes the ability of human 5-lipoxygenase-activating protein (FLAP) to activate a plant 5-lipoxygenase. The presence of an active recombinant human FLAP in the 100 000× g membrane fraction of infected Sf9 cells led to a specific increase in 9-hydroperoxyoctadecadienoic acid (9-HPOD) synthesis (+68%) or in 5-hydroperoxyeicosatetraenoic acid (5-HPETE) synthesis (+68%), after action of Solanum tuberosum tuber 5-lipoxygenase ( S.t. LOX) on linoleic acid (natural plant lipoxygenase substrate) or on arachidonic acid. On the contrary, the presence of non-transfected membranes obtained from non-infected Sf9 cells led to an inhibition of lipoxygenase activity. MK-886, a potent inhibitor of leukotriene biosynthesis, blocked the FLAP dependent S.t .LOX activation after preincubation with FLAP transfected membranes. In conclusion, this study demonstrates that a recombinant human FLAP can stimulate a lipoxygenase other than mammalian 5-lipoxygenase ( S.t. LOX) by using different polyunsaturated fatty acids as substrates.

We investigated the expression and accumulation pattern of lipoxygenase isoforms throughout the maize plant life. Two forms of lipoxygenase L1 and L2 have been identified as acidic proteins of 100 kDa (pI 6.4) and 90 kDa (pI 5.5-5.7) which accumulate in dry embryos and in various organs of maize seedlings. In young embryos, only the L2 form was detected and accumulation of L2 mRNA decreased during embryo development. Identification of lipoxygenases from in vivo and in vitro synthesized proteins indicates that similar levels of both L1 and L2 forms accumulated during treatment with abscisic acid, (ABA) gibberellic acid (GA3) and jasmonic acid (JA). However, differences in the activity of both enzymes were detected. By using an antiserum directed against purified L2 we isolated and characterized a partial cDNA clone of maize embryos encoding a lipoxygenase. The deduced amino acid sequence of L2 cDNA shares 78% identity with the rice L2 protein, and 51-56% identity with lipoxygenases from the dicotyledonous plants soybean and Arabidopsis. DNA blot analysis indicated that maize contains a family of lipoxygenase genes which are presently being characterized.

A series of experiments were designed to examine the potential induction of apoptosis by nitric oxide (NO) donors on cortical neuronal cell culture. A 24 h exposure of three different NO donors, 3-morpholinosydnonimine, S-nitroso-N-acetyl-penicillamine, and S-nitrosoglutathione, induced apoptosis as indicated by following histological (cellular and nuclear morphology) and biochemical markers (DNA oligonucleosomal fragmentation and protection by protein synthesis inhibitor).

Pisum sativum hortense cv. Solara lipoxygenase differs from previously described lipoxygenases by the presence, at optimum pH, of dual activities that can convert linoleic acid into two products, 9-hydroperoxyoctadecadienoic acid by a classical lipoxygenase activity and 2,4-decadienal by lyase activity on an intermediate peroxyl radical. This enzyme is a very labile protein and can lose activity during or after the purification procedure. In order to overcome this inconvenience, we immobilized P. sativum lipoxygenase−lyase by adsorption on talc and we explored the evolution and stability of both activities after adsorption. For lipoxygenase or lyase activity, we obtained a specific immobilization on talc with an increase in long-term stability at 4 °C in comparison to free enzyme and especially for immobilized lyase activity (60% of activity after 30 days). Immobilized enzymes appeared to be less sensitive to inhibitors than free, but the increase in IC50 values for immobilized enzymes was in fact the res...

5-Lipoxygenase products are pro-inflammatory mediators. Their roles and cellular origin in chronic inflammatory rheumatisms such as rheumatoid arthritis (RA) are poorly understood. The expression of arachidonate 5-lipoxygenase (5-LOX, arachidonate: oxygen 5-oxydoreductase; EC 1.13.11.34) and the 5-lipoxygenase activating protein (FLAP) genes in osteoarthritis and RA synoviocytes was studied at the transcriptional level by reverse transcription-polymerase chain reaction (RT-PCR) methodology. Arachidonic acid metabolism was analyzed by reverse-phase high pressure liquid chromatography. 5-LOX and FLAP mRNA were detectable using RT-PCR in all sources of synoviocytes tested. The expression of 5-LOX and FLAP mRNA led to the synthesis of 5-LOX metabolites. 12- and 15-LOX activities were also present. These LOX products can participate in inflammatory processes leading to joint destruction in RA.

Decarbonization of resin-bonded magnesia-graphite refractories, as one of the most important parameters for brick lining performance in service, has been studied kinetically in the temperature range from 1,000 to 1,400 C in air, where carbon burnout by oxygen is the dominant decarbonizing mechanism. The rate of carbon burnout was followed by gas analysis, measuring the amount of CO converted into CO{sub 2} as a function of reaction time. The experimental results have been rationalized using a mathematical model proposed for the oxidation kinetics, wherein the rate of inward diffusion of oxygen from the exterior atmosphere is predominant.

Summary Lipoxygenase activity was induced in a tobacco cell suspension culture by treatment with glycopeptide elicitors prepared from the cell walls of Phytophthora parasitica var, nicotianae, and in tobacco seedlings infected by this fungal pathogen. Upon purification and characterization, the enzyme appeared to have a molecular weight of 96000, a pl of 5.1 and a Km of 20.9 μM with linoleic acid as substrate. According to its acidic optimum pH, it belongs to type-2 lipoxygenases. Using linoleic, linolenic and arachidonic acids as substrates, the products formed in vitro by lipoxygenase were characterized. 9- and 5-hydroperoxides were the main products obtained from the C18 and C20 fatty acids, respectively, thereby indicating that a 5-lipoxygenase accounts for most of the elicitor-induced activity, since the main site of insertion of molecular oxygen is on C-5 of arachidonic acid. Small amounts of 13-hydroperoxides were also formed from the C18 fatty acids. In vitro, the strongest inhibitors of tobacco lipoxygenase were n-propylgallate and nordihydroguaiaretic acid. The possible involvement of this enzyme in signaling phenomena leading to defense induction in plants via jasmonic acid and other fatty acid-derived products is discussed.

A compound was isolated and purified from heather flowers (Calluna vulgaris) based on its ability to inhibit lipoxygenase activity. This molecule was characterized as ursolic acid by GC-MS. Ursolic acid was found to be an inhibitor of both potato tuber 5-lipoxygenase and soybean 15-lipoxygenase with IC50 values of 0.3 mM. Ursolic acid also inhibits lipoxygenase activity in mouse peritoneal macrophages at 1 microM and HL60 leukemic cells growth (IC50 = 0.85 microM) as well as their DNA synthesis (IC50 = 1 microM). The possible role of lipoxygenase inhibition in the proliferation of leukemic cells is discussed.

Maize ( Zea mays L.) seeds after 5 d germination contain at least two lipoxygenase isoenzymes, L1 and L2. Enzymes were extracted from acetone powder with 0.1 M sodium acetate (pH 4.5) buffer, supplemented with a non-ionic detergent (0.1% Brij 99) and DETAPAC (0.1 mM). The pI of L1 is 6.40 and isoelectric focusing of L2 results in two peaks with pI values in close proximity: 5.55 and 5.70. L1 and L2 are monomeric proteins of M r 100000 and 90000, respectively. Linoleic acid, 18:2( n - 6), is a good substrate for L2, but L1 has more affinity for α-linolenic acid, 18:3( n − 3). These kinetic studies could indicate a different functional role of the two isoenzymes.

Cell chemotaxis is frequently required in normal or pathological situations such as invasion, metastasis, and tumor angiogenesis and may involve many different cell types. At present, no device can simultaneously (i) make morphological observations, (ii) quantify cell migration, (iii) test multiple chemoattracting gradients, and (iv) analyze cell-cell interactions. We developed an agarose-based assay to address these questions. Two glass molds were designed, around which agarose gel could be poured to form specific well shapes. Using a vital nuclear stain (Hoechst 33258), we characterized the migration profile of adherent or suspension cells. Cells could be observed during the entire migration process. We were able to follow cells moving toward chemoattractants or being repulsed by other molecules, and we could estimate average migration speed. Using this inexpensive assay, we were able to obtain precise, reproducible results concerning the chemotactic behavior of different cell types. The resulting data differentiated between chemokinetic and chemotactic movement. Chemotactic potencies could be compared using different criteria, such as the number of attracted cells, induced speed, and morphological aspect. This improved agarose assay appears to be a reliable and inexpensive alternative to other available chemotaxis study tools.

Rheological test results on alumina-magnesia castables, containing extruded flake graphite pellets, as well as steel fibers are considered at first. After being fired at different temperatures, thermomechanical properties of such castables containing either carbon steel or stainless steel fibers have been determined, at room temperature, as well as at temperatures up to 1100°C. Those results indicate that the use of fibers improves the performances of carbon containing castables at intermediate temperatures (800 º - 1100 °C), increasing the work of fracture by 50% at 1100 °C and by 10 fold at room temperature.

As they scavenge reactive oxygen species, antioxidants were studied for their ability to interfere with apoptotic processes. However, their mechanisms of action remain unclear. In this study, we measured the expression of two Bcl-2 family members, Bax and Bcl-2, in a human endothelial like cell-line overexpressing the organic hydroperoxide-scavenging enzyme glutathione peroxidase (GPX1), in the absence of any apoptotic/oxidant stimulus. ECV304 were stably transfected with the GPX1 cDNA and used for quantification of Bax (pro-apoptotic) and Bcl-2 (antiapoptotic) mRNA and protein levels, by quantitative RT-PCR and Western-blot. We found that, compared to control cells, cells from a clone showing a 13.2 fold increase in GPX1 activity had unchanged mRNA or protein Bcl-2 levels but expressed 42.6% and 46.1% less Bax mRNA and Bax protein respectively. Subsequently to Bax decrease, the Bax/Bcl-2 ratio, reflecting the apoptotic state of the cells, was also lower in cells overexpressing GPX1. Noticeably, the mRNA and the protein level of the cell-cycle protein p53, known to activate Bax expression, was unchanged. Our study showed that overexpressing an antioxidant gene such as GPX1 in endothelial cells is able to change the basal mRNA and protein Bax levels without affecting those of p53 and Bcl-2. This phenomenon could be useful to antiatherogenic therapies which use antioxidants with the aim of protecting the vascular wall against oxidative stress injury.

Oxidative stress results from the imbalance between reactive oxygen species (ROS) and ROS-scavenging molecules. Among them, cytosolic glutathione peroxidase (GPX1) plays a major role as it reduces a large part of intracellular ROS. Endothelial cells are a barrier for potentially aggressive molecules circulating in the blood stream and, therefore, are often under great oxidative stress. Thus, we investigated the potentially protective effects of GPX1 overexpression in the endothelial cell line, ECV304. We found that chronic GPX1 overexpression delays cell growth without affecting viability or decreasing resistance to hydrogen peroxide-induced oxidative stress. As GPX1 overexpression could drain the cellular reduced glutathione (GSH) pool, we also tested the effects of extracellular GSH supplementation on cell growth. Despite its largely referenced beneficial effects for cells, GSH was toxic for ECV304 cells in a dose-dependent manner but GSH-induced toxicity was reduced in selenium supplemented cultures and completely abolished in ECV304 overexpressing GPX1, compared to control. In summary, GPX1 overexpression delays cell growth and protects them from GSH and H(2)O(2) toxicity.

We have purified two enzymic activities from flaxseed acetone powder : a lipoxygenase and a hydroperoxide dehydrase. The lipoxygenase activity belongs to an iron-containing protein having a molecular weight of 130 kDa which, upon incubation with α-linolenic acid, forms 13-hydroperoxy-9(Z), 11 (E), 15(Z)- octadecatrienoic acid. The hydroperoxide dehydrase (a 55 kDa protein) metabolizes this hydroperoxide to an allene oxide which in turn is spontaneously hydrolyzed to α-and γ-ketols. Relationships between these two enzymes were studied and results suggest an inhibition of the lipoxygenase by hydroperoxide dehydrase.

12(S)-HETE, a major lipoxygenase-derived compound from arachidonic acid is incorporated and metabolized by vascular smooth muscle cells via beta-oxidation. We have now identified for the first time in this cell type 12(S)-HETE metabolites formed by a combination of reductase and oxidation pathways. HPLC and GC-MS analysis of time-course experiments allow us to characterize two different metabolic pathways: a direct peroxisomal beta-oxidation of 12(S)-HETE leading to the formation of 16:3 (8-OH) which accumulates first and a reduction of one of the conjugated double bonds of 12(S)-HETE giving the dihydro-intermediate 20:3(12-OH) that transiently accumulates before being converted itself by peroxisomal beta-oxidation to 16:2(8-OH). Taken together these results may suggest that the transient accumulation of 20:3(12-OH) through transcellular metabolism of 12(S)-HETE may represent a part of the modulatory effect of 12(S)-HETE on vascular function.

PAF-acether can be transformed into analogs by the phospholipase D enzyme activity of Streptomyces sp. In this reaction choline is replaced by primary cyclic alcohols (acceptors). The reaction products, cyclic phospholipid and phosphatidic acid, were separated by silicic acid chromatography. This procedure enabled us to synthetize five analogs of PAF-acether, with a cyclic ring structure. The primary cyclic alcohols used in this work were: 3-(2-hydroxyethyl)-indol, OH-Et-I; 2-(hydroxymethyl)-1,4-benzodioxan, OH-Met-BZD; N -(2-hydroxyethyl)-phthalimide, OH-Et-PHT; 2-(2-thienyl)-ethanol, Th-EtOH; (1-R)-(−)-Nopol, R-NOP.

Potato tubers are shown to contain at least three lipoxygenase isoenzymes. A very efficient extraction of lipoxygenase activity is obtained when a non-ionic detergent (0.1% Brij 99) is added to the homogenization buffer. The major isoenzyme, L 1 , has been purified in an almost homogeneous form with a good yield (18%) and a high specific activity (140–160 units/mg). It is efficiently stabilized by glycerol (20%, v/v). The purified L 1 isoenzyme is slightly contaminated by an 11-lipoxygenase, both having very close p I values (4.94 and 4.99, respectively). L 1 is a monomeric protein of M r 92 000 containing one iron atom per molecule. The native enzyme is in a pseudo-axial high-spin ferric state as indicated by EPR. Acting on linoleic acid, L 1 forms 9-hydroperoxyoctadecadienoic acid (9-HPOD) almost exclusively. With arachidonic acid, 5-hydroperoxyeicosatetraenoic acid (5-HPETE) is the major product (70–75%) beside small amounts of 8(ifS)- and 9-HPETE. Due to the contaminating activity, 11-HPETE (15%) is also present. Formation of both 8( S )-HPETE and leukotriene A 4 hydrolysis products accounts for the intrinsic 8-lipoxygenase activity of the L 1 isoenzyme.

A lipoxygenase preparation was obtained from dried Lupinus albus seeds and was shown to differ from previously characterized soybean lipoxygenases in the positional specificity and pH characteristics of the dioxygenation reaction. The L. albus enzyme converted arachidonic acid into three HPETEs: 15-HPETE was the major product (60%) besides 5-HPETE (34%), and there were small amounts of 8-HPETE (6%). The enzyme had a pH optimum at 6.0 and was inactive at pH 9.O. The molecular weight of the enzyme was estimated at 71000, and pI was 5.35. The enzyme activity was inhibited strongly in the presence of lipoxygenase inhibitors, such as esculetin or BW 755 C.

Glass capillary gqs chromatography of the prostaglandins was performed on a system including an all-glass, solventless injector; thermostable methylphenylpolysiloxane glass capillary columns; and a conventional electron—capture detector fitted with a make-up gas tee. The principal stable metabolites of prostaglandin endoperoxide were separated as perfluorinated derivatives in 35min. Detection limits to equal or exceed those obtained for packed column separations and electron—capture detection. Prostaglandin endoperoxide metabolic profiles from mammalian cell cultures were obtained using this system. These profiling studies are not possible with other chromatographic methods because of inferior resolution and sensitivity.

The influence of small additions of silver on the thermodynamic properties of a dilute solution of zinc in molten tin has been studied using an electrochemical method. The Wagner interaction parameter eZnAg has been determined in the temperature range 723 to 923 K: eZnAg = 2.94 − 4353(KT).

The activity of CoO in solid solutions of CoO and MgO has been determined, in the temperature range 1273 to 1473 K, by an electrochemical method. The chemical potentials, activities, and activity coefficients of CoO and of MgO have been calculated. The mixtures exhibit slight positive deviations from ideal behavior.

The influence of small additions of copper on the thermodynamic properties of a dilute solution of zinc in molten tin has been studied using an electrochemical method. The Wagner interaction parameter eZnCu and its variation with temperature has been determined in the temperature range 723 to 923 K: e Zn Cu = −3254 K T + 2.90 .

The minima in the equilibrium deoxidation curves of Fe-Q-M systems at steelmaking temperatures are discussed in a quantitative manner in terms of a first order interaction parameter model. Two criteria for a minimum are developed and applied to the prediction of the position of minima in the deoxidation curves of several systems, including the system Iron-Oxygen-Rare Earth. Resume Les minima dans les courbes de desoxydation des systemes Fe-O-M aux temperatures elevees sont interpretes de facon quantitative au moyen d'un modele utilisant des parametres d'interaction du premier ordre. Les auteurs presentent deux criteres qui determinent la position des minima et les appliquent a plusieurs systemes, et en particulier, au systeme Fer-Qxygene-Terres Rares.a : Raoultian activityf : Henrian activity coefficienth : Henrian activityei,j : interaction parameter of element j on element i.K: equilibrium constant of deoxidation reaction%M : weight per cent metal in solution%O : weight per cent oxygen in solut...

5,8,11-Icosatrienoic acid (20:3 n -9), a fatty acid associated with platelet hyperactivity, was oxygenated by platelet lipoxygenase. The end-product of this pathway was purified by high-performance liquid chromatography (HPLC) and characterized as 12-hydroxy-5,8,10-icosatrienoic acid [12-OH-20:3(5,8,10)] by capillary gas-liquid mass spectrometry. When tested upon platelet aggregation, 12-OH-20:3(5,8,10) exhibited a biphasic effect. At low concentrations (below 5 × 10 −7 M) it potentiated aggregation but inhibited it at higher levels, a pattern similar to that obtained with prostaglandin E 2 . However, since the amounts of 12-OH-20:3(5,8,10) generated under thrombin stimulation are in the range of concentrations with potentiating effects, it seems that the 12-OH derivative is responsible for the hyperaggrebility of 20: 3 n -9-rich platelets.

The calcium ionophore A 23187 (iono.) induced a change in light transmission (LT) of thrombasthenic (thr.) platelets (pl.) either in plasma or washed and resuspended in buffer. This was not due to aggregation, but was associated with the formation of a central contractile gel mass and central apposition of organelles ; lactic dehydrogenase determination showed no evidence of platelet lysis. After incorporation of [ 14 C]-arachidonic acid into the platelet phospholipid pool, stimulation with the iono. showed similar profiles of oxygenated products for both normal and thr. pl., providing evidence for a normal activity of phospholipase(s) in thr. pl. under these conditions. The iono. induced normal thromboxane (TX) synthesis and serotonin (5HT) release in thr. pl.; the TX formation but not the accompanying change in LT, was inhibited by aspirin. The action of the iono. on thr. pl. thus provides a natural model for studying TX formation and 5HT release in the absence of aggregation.

Mouse peritoneal macrophages synthesize 6 monohydroxylated eicosatetraenoic acids when incubated with exogenous arachidonic acid. These compounds were identified by chromatographic techniques (high pressure liquid chromatography and high efficiency glass capillary column gas chromatography and mass spectrometry. The chromatographic and spectrometric data are presented. These results show that peritoneal macrophages constitute one of the best systems to study in evaluating the metabolism of oxygenated products of arachidonic acid.

Mouse peritoneal macrophages were incubated at 37°C for 30 min with arachidonic acid (all- cis -5,8,11,14-eicosatetraenoic acid). Oxygenation of arachidonic acid in mouse peritoneal macrophages occurs by two major pathways: fatty acid cyclooxygenase and lipoxygenase. The major metabolite of the latter is 12-hydroxy-5,8,10,14-eicosatetraenoic acid which was identified by gas liquid chromatography on high resolution glass capillary column and mass spectrometry.

Publisher Summary This chapter describes the open tubular glass capillary gas chromatography for separating eicosanoids. Gas-liquid chromatography involves a partition of the molecules of the sample components to be analyzed between the stationary liquid phase and the carrier gas within the column. In traditional packed columns, the low speed of diffusion of the sample components between the two phases is the limiting factor of the efficiency (i.e., separation power) and of the time of analysis; open tubular columns shorten both, and provide a gain in sensitivity of ×100. For biochemical separation glass capillary columns are required as for packed columns. The various procedures are presented for the preparation of capillary columns. Capillary tubes, either soda-lime for polyglycol phases, such as Carbowax, or borosilicate glass for other phases, such as polysiloxanes, are drawn by a machine. Additionally, some of the practical details or modifications of the original methods are discussed that improve the column preparation.

Radioimmunoassays of platelet prostaglandins E1 and F1 alpha in platelet rich plasma or platelet suspension, demonstrate that both PGE1 and PGF1 alpha are present at higher concentrations than prostaglandins E2 and F2 alpha. Gas chromatography--mass spectrometry determinations of prostaglandins E1 and E2 in resting washed platelets confirm this difference. Lastly, there is a greater incorporation of [1--14C] acetate into prostaglandins E1 and F1 alpha compared to that into prostaglandins E2 and F2 alpha.

Prostacyclin (PGI2) synthesis seems to be one of the major physiological mechanisms involved in regulating platelet and vessel wall interactions. PGI2 is produced in large amounts by vascular endothelial cells, and vascular smooth muscle cells (SMC) also produce significant quantities. The capacity of SMC to produce PGI2, especially after endothelial injury, seems to be of importance. It is probably this type of situaton that is involved in the atherosclerotic process: experimental atherosclerosis in rabbits has been associated with a severe decrease in PGI, synthesis by arteries. Lipid peroxide accumulation within the arterial wall or in the plasma may also be involved in this process. Using arterial SMC in culture, we demonstrate here that, in comparison with healthy cultured cells, cells originating from atherosclerotic aorta have a decreased capacity to produce PGI2. The results were obtained using biological and radiochemical techniques and were confirmed by GC-MS. They suggest a potential role for PGI2 in inhibiting the atherosclerotic process.

Arachidonic acid can be transformed into a series of HPETEs by the lipoxygenase enzyme activity of mouse peritoneal marcrophages. These resulting HPETEs inhibit some mouse lymphocyte responses. When mice are injected with 15- l -HPETE, their splenocytes show a decreased [ 3 H]thymidine uptake after lectin stimulation.

In addition to the well established cyclooxygenase pathway, cultured aortic smooth muscle cells convert arachidonic acid to several polar metabolites identified by high performance liquid chromatography and gaz chromatography-mass spectrometry. 15-Hydroxyeicosatetraenoic acid, 12-Hydroxyeicosatetraenoic acid and 5-Hydroxyeicosatetraenoic acid are the major products formed. These observations indicate that the rabbit aortic smooth muscle cells are a potential source of lipoxygenase products and raise the possibility that this pathway of arachidonic acid metabolism can influence the biological functions of arterial myocytes under normal and pathological conditions.

A release of prostaglandin (PG) has been demonstrated in lymphocyte culture supernatants. The amount of PG produced is strikingly increased in mixed cultures between allograft donor and recipient. This phenomenon is not yet detectable after 6 h of culture, appears at 24 h and reaches its maximum at 48 h. Little or no increase in PG production is found in the supernatant of primary mixed lymphocyte cultures (i.e. without previous allograft) at least in the first two days of culture. The difference between allografted and control animals begins at day 6 after grafting, reaches a maximum at day 12, remains high until day 20 and decreases thereafter. This increased amount of PG in mixed cultures between donor and recipient spleen cells is probably, at least to a large extent, produced by macrophages. Evidence for this interpretation includes the following observations: (a) cells responsible for the increase are adherent cells and (b) the phenomenon is no longer found following a treatment of spleen cells with silica. When mouse peritoneal macrophages (or adherent spleen cells) are incubated in vitro with supernatants of mixed cultures between allograft donor and recipient, their PG production is considerably increased. Hence, it is suggested that the above-described phenomenon could result from the stimulation of macrophages by lymphokines released in mixed cultures following allografts. If such a release of PG takes place within the graft, it may play a regulatory role in the control of the magnitude of the anti-allograft immune response.

Human, monkey and rat alveolar macrophages (AM) release PAF-acether in a dose-dependent fashion in the presence of 1 to 5 microgram/ml ionophore A 23187 (2.5 pmol of PAF-acether from 2.5 x 10(5) cells) but not in the presence of zymosan. Arachidonic acid (AA) metabolites released from AM from these species were studied. Thromboxane A2 TxA2) - detected by its action on rabbit arteries - was released from human, monkey and rat AM upon addition of 0.5 mM AA. This release was inhibited by aspirin and indomethacin. Lipoxygenase and cyclooxygenase AA metabolites from rat AM were identified using high efficiency glass capillary column gas chromatography coupled to mass spectrometry. The cyclooxygenase metabolites PGF2 alpha, E2 and D2 and TxB2 were identified. The lipoxygenase-dependent AA metabolites were explored using aspirin-pretreated AM. Only 12 HETE was found. These data indicate that AM secrete several substances with bronchoconstrictive activity: PGF2 alpha, D2, TxA2 and PAF-acether. Therefore an active role of AM in human and experimental bronchoconstriction must be considered.