Phosphatidylserine-related adhesion of human erythrocytes to vascular endothelium

In pathological conditions such as sickle cell disease, falciparum malaria and diabetes, an abnormal adherence of erythrocytes to endothelium is concomitant with loss of phospholipid asymmetry resulting in phosphatidylserine (PS) exposure. We have investigated the involvement of PS in this interaction by studying adhesion of human erythrocytes, treated with Ca2+-ionophore A23187 in combination with N-ethylmaleimide, to human umbilical vein endothelial cells in a flow-based assay. Results showed that erythrocytes which exposed PS, massively adhered to HUVEC in a Ca2+-dependent manner. This adhesion was inhibited by PS liposomes and by annexin V, giving clear evidence of the PS dependence of these interactions.

A flow cytometric method using Hoechst 33342 and propidium iodide for simultaneous cell cycle analysis and apoptosis determination in unfixed cells

A flow cytometric method to detect apoptotic cells is described. This method is based on the detection of differences in chromatin condensation with Hoechst 33342 as a probe and the detection of dead cells with propidium iodide as a probe for membrane damage. By this method it was possible to detect, in the same sample and at the same time, intact cells, cells undergoing apoptosis, and dead cells resulting from apoptotic and/or necrotic processes. The method was successfully applied to the detection of apoptotic cells in two human cell models: cultured polymorphonuclear cells and the U937 cell line treated with antitumoral drugs. Staining specificity for apoptotic cells was controlled by cell sorting of the presumed apoptotic population, followed by morphologic examination or DNA analysis of the sorted populations. The usefulness of such a method is discussed in terms of applications in the analysis of heterogeneous clinical samples, populations with low DNA degradation during apoptosis, and cell cycle position of the apoptotic cells.

Flow cytometry CD45 gating for immunophenotyping of acute myeloid leukemia

A flow cytometry method has been introduced into the routine investigation of whole bone marrow samples following red blood cell lysis on the basis of a primary CD45/side scatter (SSC) gating procedure. Blast cells were first identified by CD45/SSC gating in 74 cases of acute myeloid leukemia (AML) and the results were compared to a conventional FSC/SSC gating procedure and to MGG-staining smears. The percentages of blast cells in these samples as defined by the morphological analysis of MGG smears correlated better with the values determined by CD45/SSC gating (r = 0.94) than with the blast cell counts recorded with FSC/SSC gating (r = 0.76). These findings were not surprising because while CD45 expression was regularly lower on leukemic blasts than on normal lymphoid and monocytic cells, the FCS/SSC characteristics of these populations were overlapping. In 53 samples, the blast cell populations were also analyzed with a panel of FITC-conjugated monoclonal antibodies that were utilized in double labeling with CD45-PE. We show that the CD45/SSC gating procedure improved phenotypic determination of the blast cells in three ways: (1) by discriminating between leukemic blast cells and residual normal cells; (2) by excluding normal cells from the phenotypic analysis of leukemic blast cells; and (3) by identifying blast cell heterogeneity in many cases of leukemia on the basis of different CD45 display. Moreover, this immunophenotyping procedure on whole bone marrow samples also allowed an efficient discrimination between the various cell lineages and facilitated the analysis of leukemic blasts present in low proportions.

Modalities of synthesis of Ki67 antigen during the stimulation of lymphocytes

The antibody Ki67 is currently used to evaluate the proliferative fraction of solid tumors and some hematological malignancies. We have used phytohemagglutinin (PHA)-stimulated peripheral blood lymphocytes as a model to study the entry of quiescent cells into cell cycle and to follow their progress to the next cycle. Flow cytometric analysis of lymphocyte samples stained with the antibody Ki67 and a DNA marker has allowed us to follow the expression of Ki67 antigen (Ki67 Ag) as a function of the position of the cells in the cell cycle. The use of drugs blocking the stimulated lymphocytes in different phases of the cell cycle permitted us to demonstrate that Ki67 Ag expression started from the beginning of the first S phase. The level of Ki67 Ag increased during S phase until mitosis, when its expression was maximal. After division, the cells in G1 phase showed a decrease in Ki67 Ag expression (possibly corresponding to degradation) until they reentered S phase, when the level of Ki67 Ag increased again. The results confirm that the expression of Ki67 Ag is related to the proliferative state of the cells and suggest that it may be used to determine the proliferative cell fraction in hematopoietic tissues.

Levels of plasma thrombomodulin are increased in atheromatous arterial disease

The plasma thrombomodulin (TM) level depends on the integrity of the endothelium and the clearance of the molecule. In several different pathological conditions, plasma TM levels increase with damage to the endothelium. We studied plasma TM levels in patients with various localizations of atheromatous arterial disease who had normal serum creatinine levels. Two groups of patients had a single symptomatic localization, which was either peripheral occlusive arterial disease (POAD) or ischemic heart disease (IHD) and a third group of patients had multiple symptomatic localizations (polyvascular). We compared the plasma TM levels with the plasma levels of other specific markers of endothelial cell activation such as: prostacyclin (PGI2), tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI-1). Plasma TM levels were significantly increased in all three individual groups and when all patients were considered (total patients), as compared with normal controls. When all patients were considered, there was a significant positive correlation between plasma TM levels and t-PA and between plasma TM levels and PGI2. A significant positive correlation was also found between the plasma TM levels and PAI-1 for patients with POAD. Thus, our findings suggest that an increased influx of TM into the plasma may be caused by endothelial cell damage in patients with atheromatous arterial disease. However in our study, the plasma TM levels obtained were similar for all three types of atheromatous arterial disease. Though plasma thrombomodulin is a marker of endothelial cell injury, it cannot be of a clinical interest until its levels are related to the extend of the atheromatous lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Vitronectin expression and interaction with receptors in smooth muscle cells from human atheromatous plaque

Vitronectin (VN) is a plasma glycoprotein that promotes cell attachment and induces migration of human smooth muscle cells (SMCs) in culture. VN has been observed to accumulate in human atherosclerotic plaques, although its origin and role in atherosclerosis are not yet established. In the present experiments, synthesis of VN by intimal cells and its colocalization with receptors, alphavbeta3 and alphavbeta5, were studied by in situ hybridization and immunohistochemistry on 15 human atherosclerotic plaques from carotid arteries obtained after surgery. Strong VN protein and mRNA expression was observed in the intima and in the media. In the intima, VN mRNA expression was colocalized with SMCs, indicating that these cells produce VN, which may account for its accumulation in atherosclerotic plaques. In SMCs in culture, immunoprecipitation after metabolic labeling demonstrated that human SMCs do synthesize vitronectin. Confocal microscopic examination showed that VN colocalized with its receptors, alphavbeta3 and alphavbeta5, in the atherosclerotic intima. However, the distribution of the VN receptors on SMCs in culture in contact with VN was different. These observations suggest that VN plays various parts in atherogenesis via different SMC membrane receptors.

Circulating endothelial cell markers in peripheral vascular disease: relationship to the location and extent of atherosclerotic disease

We examined the relationship between specific endothelial cell markers soluble E-selectin, von Willebrand factor and soluble thrombomodulin and the location or extent of atherosclerosis by analysing plasma samples from 200 patients with symptomatic peripheral vascular disease and 213 age- and sex-matched asymptomatic control subjects. Using ELISAS, we found increased von Willebrand factor and thrombomodulin (both P < 0.0001) in the patients relative to the control subjects, but no significant change in soluble E-selectin. Soluble thrombomodulin was increased in patients with disease at one locus (i.e. of the carotid or iliac/femoral arteries), with an additional significant increase in patients with disease at multiple loci (i.e. any combination of carotid, coronary or iliac/femoral artery disease). No marker differentiated carotid artery disease from iliac/femoral artery disease. We conclude that von Willebrand factor is a marker of generalized atherosclerosis, but that soluble thrombomodulin is related to the extent of disease. Further research into these endothelial cell products are warranted to explore their diagnostic and/or prognostic potential.

Study of the effect of metformin on platelet aggregation in insulin-dependent diabetics

The role of metformin on platelet aggregation was studied in subjects affected by relatively well controlled type 1 diabetes. 1700 mg of metformin were added to their usual daily treatment; nothing else was changed. Patients were trained to monitor their own glycaemia and presence of degenerative retinopathy was proved. Before the administration of metformin and on day 21, the platelet induced by 1.25, 2.5 and 5 mumol of ADP and by collagen was studied. Fibrinogen, cholesterol, triglycerides, glycosylated haemoglobin and mean blood glucose levels did not show any significant modification after treatment but the maximum aggregation induced by ADP was significantly decreased; the inhibition of aggregation was particularly sensitive for low doses of ADP. No significant correlation was found between the variations in metabolism data and the reduction of the amplitude of platelet aggregation. Metformin, added to the usual treatment undergone by a diabetic treated with insulin, seems to affect platelet aggregation independently of other metabolic factors.

The labelling of proliferating cells by Ki67 and MIB-1 antibodies depends on the binding of a nuclear protein to the DNA

The antigen Ki-67 Ag, regarded as a marker for proliferating cells, was identified as a protein(s) (pKi-67) which can exist free or associated with DNA as evidenced by DNA digestion of cells before or after immunolabeling with Ki-67. The dual nature of this antigen was also supported by reconstitution of Ki-67 Ag from purified DNA and nuclear proteins extracted from the K562 cell line. The immunoreactivity of the resulting complexes was examined in solution using Ki-67 and MIB-1 antibodies. The interaction between Ki-67 or MIB-1 antibodies and pKi-67 was enhanced in the presence of undegraded ds DNA, indicating that ds DNA modulates the conformation of pKi-67 and that the altered conformation of pKi-67 is more reactive than the pure protein to both Ki-67 and MIB-1 antibodies.

Study of the apoptosis induced in vitro by antitumoral drugs on leukaemic cells

A flow cytometric method for simultaneous apoptotic cell detection and cell cycle analysis was applied on the U937 cell line. Four antitumoral drugs currently used in the treatment of acute myeloid leukaemia were studied in vitro: DNR, IDR, MITO and Ara-C. Our results show a dissociation between the cytostatic effect (the block in the cell cycle observed for low drug concentrations) and the cytotoxic effect (the induction of apoptosis induced by higher concentrations) for all the tested molecules. Low concentrations of Ara-C induced a block in the S phase while higher concentrations (>10(-7) M) induced apoptosis at the G1-S boundary. Low concentrations of anthracyclines (<40 nM DNR and <20nM IDR) induced a block in G2 without apoptosis. Apoptosis was induced in G1 and/or early S phases by higher concentrations of anthracyclines. The concentration inducing 50% apoptosis (IC50) was found to be, respectively, 200 and 40 nM for DNR and IDR. Analysis of MITO-treated cells showed a parallel increase in the percentages of S phase and apoptotic cells. However, the bivariate analysis showed that apoptosis did occur in a population with G1 DNA content. For two other drugs (CAM and COLC), apoptosis occurred for the same concentrations and in the same phase as the block (in S and G2M, respectively). The IC50 of MITO was found to be 100 nM. Cotreatment of the cells with colchicin and either Ara-C or IDR showed that the passage through mitosis was not necessary for the completion of apoptosis at the G1-S boundary. Short incubations of U937 cells with high concentrations of anthracyclines were found to be efficient in inducing further apoptosis. We conclude that, for all the assayed molecules, the cytotoxic and/or cytostatic effects of the antitumoral drugs tested greatly depend on the concentrations used and that, depending on their in vivo pharmacokinetics, the induction of apoptosis could be an important mechanism of action for some of these drugs.

Caspase activation is an early event in anthracycline-induced apoptosis and allows detection of apoptotic cells before they are ingested by phagocytes

An increasing number of methods are being described to detect apoptotic cells. However, attempts to detect apoptotic cells in clinical samples are rarely successful. A hypothesis is that apoptotic cells are cleared from the circulation by phagocytosis before they become detectable by conventional morphological or cytometric methods. Using LR73 adhering cells as phagocytes in a model of in vitro phagocytosis, we found that phagocytosis of daunorubicin (DNR)-treated U937, HL60, or K562 leukemia cell lines occurred prior to phosphatidylserine externalization, DNA hydrolysis, chromatin condensation, nuclear fragmentation, or mitochondrial potential alteration. Moreover DNR-treated K562 cells were eliminated by phagocytes while apoptosis was never observed by any of the above methods. By contrast, using a fluorometric batch analysis assay to detect caspase activity in ceramide- or DNR-treated cells (fluorogenic substrate for caspase), we found that caspase activity increased in apoptosis-committed cells before they were detected by flow cytometry or recognized by phagocytes. Similarly a caspase activity increase was detected in circulating mononuclear cells of luekemic patients 15 h after the beginning of anthracyclin treatment. We suggest that recent findings on enzymatic events (caspase activation) occurring in the early events of apoptosis must now allow the development of new markers for apoptosis, irrespective of the morphological features or internucleosomal fragmentation which are late events in apoptosis.

A stage classification for prognosis in adult acute myelogenous leukaemia based upon patients' age, bone marrow karyotype and clinical features

In 71 adult acute myelogenous leukaemia (AML) cases, the relationship between well-known prognostic features and complete remission (CR) rate and survival was studied. These features were: (i) bone marrow karyotype classified NN, AN, AA according to Sakurai & Sandberg (5); (ii) patients' age; (iii) clinical 'negative prognostic features' (NPF): previous history of preleukaemia, septicaemia or pneumonia, hyperleucocytosis, associated pathology (diabetes, obesity, renal insufficiency etc.). 59 years of age was found to be a frontier between 2 homogeneous groups having quite different prognosis. The NN/AN/AA classification had good prognostic value (CR rate and survival) in patients under 59 years, but not in older patients. In those patients over 59, a significant difference in CR rate and survival appeared between cases with NPF and those without. For each feature having an established relationship to survival, a panel of prognostic points was determined as follows: age over 59 (1 point), AA karyotype in patients under 59 (2 points), NPF in patients over 59 (1 point). Using this stage classification, it was possible to classify every case into 1 of 3 groups (i.e.: 0 points, 1 point, 2 points). The life-table analysis of these 3 groups showed very significant differences. The median survival times were 18.5 months, 5.2 months and 1.3 month, for the 0-point group (26 cases), the 1-point group (19 cases) and the 2-point group (26 cases), respectively.

Serum fatty acid profiles in type I and type II diabetes: metabolic alterations of fatty acids of the main serum lipids

Fatty acid profiles of various lipid fractions were determined in carefully selected insulin-dependent and non-insulin-dependent diabetics to assess relationships between serum fatty acid composition and type of diabetes. Clear-cut hypertriglyceridemia with slight hypercholesterolemia was found in both diabetic types. The decrease of lignoceric acid in sphingomyelin is the only alteration found in both types of diabetes. In the insulin-dependent diabetics, there were increases in levels of oleic acid and of alpha-linolenic acid in esterified cholesterol, and in levels of alpha-linolenic acid in the triglyceride fraction. In the non-insulin-dependent diabetics, there were increases in levels of oleic acid and total monounsaturated fatty acids in the triglyceride fraction and there was an increase in levels of saturated fatty acids and a decrease in levels of polyunsaturated acids in phosphatidylcholine; in sphingomyelin, dihomogamma-linoleic acid levels were enhanced. Arachidonic acid levels were normal in our patient population.

Changes in phospholipid composition of blood cell membranes (erythrocyte, platelet, and polymorphonuclear) in different types of diabetes--clinical and biological correlations

A variety of disorders of erythrocyte, platelet, and polymorphonuclear leukocyte (PMN) functions have been described in diabetes. The phospholipid composition of erythrocyte, platelet, and PMN membranes from controls and from type I and II diabetics was investigated in this study. Phospholipids were determined by densitometry using the molybdenum blue reagent. In diabetics, the relative abundance of phosphatidylethanolamine (PE) increased in all cell types studied, whereas those of sphingomyelin (Sph) and phosphatidylcholine (PC) were decreased in platelets and PMN. The percentage of phosphatidylserine (PS) was reduced in erythrocytes but increased in platelets. The level of Sph in PMN was significantly lower in type I than in type II diabetics. Moreover, the longer the duration of diabetes and the poorer the metabolic control, the greater the decrease in Sph. Rheological parameters, which reflect the behavior of red blood cells (RBC), were correlated with the alteration in PE/PS ratio in these cells.

Automated reticulocyte counting and immature reticulocyte fraction measurement. Comparison of ABX PENTRA 120 Retic, Sysmex R-2000, flow cytometry, and manual counts

We evaluated reticulocyte counting and measurement of immature reticulocyte fraction (IRF) with the ABX PENTRA 120 Retic blood analyzer on 300 blood samples. Reticulocyte counts were compared with those obtained by visual counting of 2,000 RBCs, by the TOA (Kobe, Japan) Sysmex R-2000 and a flow cytometry method. The parameters analyzed were the percentages of reticulocytes on all analyzers and the IRF with different modalities. The Retic Count kit (Becton Dickinson, San Jose, CA) was used with the Coulter (Hialech, FL) XL, and a mean channel of fluorescence (MCF) was calculated to fit the reticulocyte maturation. Reticulocyte counting with the ABX (Montpellier, France) PENTRA 120 Retic showed excellent precision and linearity with no significant carryover. Reticulocyte counts were stable after blood storage for 72 hours at 4 degrees C but not at room temperature (RT). IRF parameters values were stable for only 8 hours at 4 degrees C and 6 hours at RT. Comparisons of the methods showed good intraclass correlation (RI) for reticulocyte percentages between ABX PENTRA 120 Retic and Sysmex R-2000, ABX PENTRA 120 Retic and flow cytometry, Sysmex R-2000 and flow cytometry, and ABX PENTRA 120 Retic and manual counting. IRF values were correlated between fluorescence rates and RNA content, but in each case, low RI values were found, showing that Sysmex and ABX IRF values were not concordant. We obtained a significant correlation between mean fluorescence index and the MCF measured by flow cytometry, but the 2 methods were not concordant using the RI. The ABX PENTRA 120 Retic is a good instrument for analyzing reticulocyte count and percentage and allows a good analysis of IRF with several modalities.

Rheological properties of commonly used plasma substitutes during preoperative normovolaemic acute haemodilution

Preoperative normovolaemic acute haemodilution (PNAH) is used to reduce major blood loss during elective surgery. Considerable attention has been paid to colloid osmotic pressure, index of diffusibility and intravascular half-life of the currently available substitutes, but there is little information on their rheological properties from in vivo studies. Forty patients undergoing elective aortic reconstruction were given 4% human albumin (HA), 3.5% dextran 40 (Dxt 40), 6% dextran 60 (Dxt 60), 6% hydroxyethylstarch 200 (HES) or modified fluid gelatin (Gel) during PNAH to produce a packed cell volume (PCV) of approximately 30%. Mean volumes of more than 1000 ml were infused. Blood samples were obtained before infusion, immediately after, and 1.5 h after the end of haemodilution. The following variables were measured: PCV, plasma viscosity, whole blood viscosity at measured and corrected PCV (0.45), and erythrocyte aggregation. Haemodynamic and metabolic variables were determined at the same time. The five substitutes had very different effects on red blood cell aggregation and low shear rate viscosity at corrected PCV. Red blood cell aggregation was reduced in the presence of HA, Dxt 40, but was increased moderately to markedly in the presence of the other substitutes in the following order: HES < Dxt 60 < Gel. The influence of the rheological conditions on tissue oxygenation was assessed by measuring the concentration of lactic acid; this was unchanged after PNAH with HA or Dxt 40, but was increased in the presence of HES, Dxt 60 or Gel.

Three months supplementation of hyperhomocysteinaemic patients with folic acid and vitamin B6 improves biological markers of endothelial dysfunction

Hyperhomocysteinaemia is a risk factor for premature atherosclerosis and venous thromboembolic disease. Supplementation with folic acid and vitamin B6 has been shown to decrease plasma homocysteine but data fail to assess an effect on the progression of vascular disease. We measured plasma homocysteine and two markers of endothelial injury (plasma soluble thrombomodulin and von Willebrand factor) at baseline and after 3 months of treatment with folic acid and vitamin B6. After this treatment there was a significant decrease in fasting soluble thrombomodulin (-15 ng/ml, 95%CI 5-22.2). Von Willebrand factor was significantly raised after methionine load at baseline but did not significantly rise after supplementation.

Intercalation of anthracyclines into living cell DNA analyzed by flow cytometry

Anthracyclines (ANT) are used in the treatment of leukemia and other cancers. These drugs have been shown to intercalate between the strands of DNA. In the present study, we show that the amount of ANT intercalated into DNA can be determined by measuring the fluorescence resonance energy transfer (FRET) between Hoechst 33342 (H33342) and ANT bound to DNA. The transfer efficiency was found to depend on the amount of disposable ANT but was independent of the amount of H33342 bound to DNA over a wide range of H33342 concentrations. The method was adapted for flow cytometric measurement of FRET in whole living cells and was used to evaluate the degree of intercalation of daunorubicin (DAU) and idarubicine (IDA) into DAU-sensitive and DAU-resistant leukemic cell lines. ANT intercalation into DNA was affected by factors which modify the intracytoplasmic concentration of ANT, and it was shown that the action of ANT and the resistance to ANT could not be attributed solely to the intercalative effect of the drugs. The method has advantages over previously described methods and represents a useful complementary tool in studies on the mode of action of ANT and the mechanisms of chemoresistance.

Evaluation of four methods of DNA distribution data analysis based on bromodeoxyuridine/DNA bivariate data

Four published methods of DNA-content histogram analysis (those of Fried, Dean and Jett, simplified Dean, and Fox) were compared using a double labeling of different cell populations. Partially synchronized and asynchronous cell populations were incubated with bromodeoxyuridine (BrdUrd) and then stained with an anti-BrdUrd monoclonal antibody and propidium iodide (PI). The fractions of cells in the G1, S, and G2 + M phases were calculated by each method and compared with those derived from G1, S, and G2 + M areas plotted on BrdUrd/DNA bivariate histograms, taken as the "true" values. This procedure enabled an optimal choice of method for a given cell population.

Fibrinogen synthesis by megakaryocyte rich human marrow cell concentrates

A rapid method is described for the production of a human marrow cell suspension highly enriched in megakaryocytes. These concentrates were incubated with radiolabelled amino-acids, and cell lysates were then analysed for fibrinogen synthesis. Neosynthesized proteins were detected by immunoprecipitation, immuno-affinity chromatography and electrophoresis. Fluorography of the electrophoresis gels showed three radioactive bands corresponding to the three chains of cold fibrinogen. Immunoblotting and autoradiography of bidimensional, nonreduced-reduced electrophoresis gels showed that these three proteins were joined by disulfide bonds in the cell. These results suggest that megakaryocytes synthesize fibrinogen, and imply that platelet fibrinogen is of megakaryocytic origin.

Phospholipid and fatty acid composition of erythrocytes in type I and type II diabetes

Different data have been reported concerning modifications of the erythrocyte lipid composition in the different types of diabetes. The heterogeneity of diabetes could be a cause for such differences. Ten type I and ten type II diabetics were carefully selected. The patients were poorly controlled (the mean glycosylated hemoglobin was 12.8% +/- 0.7%); their mean age was 54 +/- 5 years, with a mean duration of diabetes of 18 +/- 4 years. One half of them had severe diabetic complications (nephropathy, retinopathy, and/or polyneuropathy). The diabetics were compared with ten controls. The phospholipid composition was determined by HPTLC analysis, and the fatty acid moieties of the total phospholipids were measured by gas liquid chromatography associated with mass spectrometry. Under well-defined experimental conditions, these results demonstrated a slight, but significant (P less than .05), increase in the phosphatidylethanolamine (PE)/phosphatidylserine (PS) ratio using a Ninhydrin quantitation method; there was also an increase in two minor lipids content (phosphatidylinositol, phosphatidic acid) and the appearance of a lysolipid (lysoPE) in the patients. Whatever the type of diabetes, the red blood cells of diabetics showed no significant differences in their fatty acid contents.

Effect of pentoxifylline on apoptosis of cultured cells

Apoptosis or programmed cell death (PCD) was measured in two human cell models by flow cytometric analysis. Blood neutrophils underwent spontaneous apoptosis in short-term culture. Pentoxifylline (PTX) inhibited spontaneous neutrophil PCD. We confirmed that granulocyte/macrophage colony-stimulating factor (GM-CSF) inhibited apoptosis of polymorphonuclear neutrophils. Treatment with both GM-CSF and PTX did not increase the inhibition of PCD by either GM-CSF or PTX alone. Because apoptosis could be due to the accumulation of H2O2 in the culture medium, and because PTX has been described to reduce peroxide production, we studied the effect of adding catalase to the medium. Catalase reduced the neutrophil apoptosis and this effect was cumulative with the effect of PTX. Camptothecin, an inhibitor of topoisomerase I, induces a block in the S-phase of the cell cycle followed by apoptosis of the U937 cell line. This drug-induced apoptosis was partially inhibited by PTX, whereas the S-phase cell block was not affected. In conclusion, PTX was found to inhibit apoptosis in two different human cell types. In neutrophils, this effect appears to occur regardless of the inhibition of phosphodiesterase activity and inhibition of H2O2 release.

Endothelial dysfunction during acute methionine load in hyperhomocysteinaemic patients

Hyperhomocysteinaemia has been associated with arterial and venous thrombosis possibly by causing damage to the endothelium. We hypothesised that an oral load in methionine, that increases plasma homocysteine, would also result in an increase in biological markers of endothelial or platelet dysfunction. Then we investigated two groups of patients with arterial or venous occlusive disease: 17 with hyperhomocysteinemia and 12 without hyperhomocysteinemia. We measured in both groups plasma soluble thrombomodulin, von Willebrand factor, P-selectin and tissue factor plasma inhibitor before and 6 hours after a load with 100 mg/kg oral methionine. Methionine load resulted in a significant increase in von Willebrand factor in both groups (P<0.02), suggesting that endothelial dysfunction occurs during the load.