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M Gawaz

Publications and source records attributed to M Gawaz.

At least 55 records · Page 3Linked to original sources
PubMed1996

[Antithrombocytic effectiveness of magnesium].

Platelet activation and subsequent intravascular thrombus formation play a central role in the pathophysiology of acute coronary syndromes. Extracellular magnesium has an antithrombotic action due mainly to its antiplatelet effect. High concentrations of magnesium inhibit platelet aggregation and adhesion in vitro and reduce the generation of prothrombotic eicosanoids. In addition, magnesium modulates the intracellular platelet activation cascade and decreases calcium influx. The function of major platelet membrane receptors, such as the fibrinogen receptor GP-IIb-IIIa and P-selectin are also inhibited by extracellular magnesium. Intravenous magnesium inhibits platelet function in vivo-additive to aspirin. The antiplatelet effect of intravenously administered magnesium might be of benefit to patients with acute coronary syndromes when given before the development of an occlusive thrombotic plug.

Coronary Thrombosis↗
PubMed1996

Increased neutrophil-platelet adhesion in patients with unstable angina.

BACKGROUND: Neutrophil-platelet adhesion may occur as a consequence of platelet activation. The role of this heterotypic adhesion in ischemic disorders is poorly understood thus far. METHODS AND RESULTS: Systemic venous blood samples were taken from 25 patients with stable angina pectoris and 25 patients with unstable angina pectoris. Neutrophil activation and neutrophil-platelet adhesion were evaluated by two-color flow cytometry. Patients with unstable angina showed a significant increase in neutrophil-platelet adhesion compared with patients with stable angina (mean +/- SEM, 132.1 +/- 20.5 versus 29.8 +/- 4.7 anti-glycoprotein IIb/IIIa mean fluorescence intensity, P = .0001). Systemic neutrophil activation was found in patients with unstable angina compared with those with stable angina assessed by cell surface CD11b expression and shedding of L-selectin (115.6 +/- 10.3 versus 74.0 +/- 6.3 anti-CD11b mean fluorescence intensity, P = .002; 49.8 +/- 6.0 versus 72.1 +/- 4.0 anti-L-selectin mean fluorescence intensity, P = .006). Markers of neutrophil activation were related to the extent of neutrophil-platelet adhesion (CD11b: r = .5, P = .0005; L-selectin: r = .42, P = .012). In vitro studies revealed that binding of purified platelet membranes to control neutrophils caused a dose-dependent increase in CD11b surface expression, a decrease in surface L-selectin, and the release of superoxide anions. CONCLUSIONS: Thus, this study demonstrates that increased neutrophil-platelet adhesion may contribute to neutrophil activation in unstable angina.

Aged↗
PubMed1996

Platelet function and platelet-leukocyte adhesion in symptomatic coronary heart disease. Effects of intravenous magnesium.

Spontaneous P-selectin surface expression on platelets and platelet-leukocyte adhesion was increased in patients with symptomatic coronary heart disease (n = 12) compared to normal controls (n = 10) (p < 0.05). ADP-induced P-selectin expression and platelet-leukocyte adhesion was also enhanced in the patient group (p < 0.05). Administration of intravenous Mg2+ significantly reduced both platelet surface expression of P-selectin and platelet-leukocyte adhesion ex vivo (p < 0.02). The effect of extracellular Mg2+ was evaluated in in vitro experiments. Both in whole blood and in isolated neutrophil suspension Mg2+ inhibited platelet adhesion to neutrophils dose dependently with half maximal effects at 4 mM. Moreover, Mg2+ inhibited adhesion of isolated platelet membranes to neutrophils. We conclude that platelet function is altered in symptomatic coronary heart disease and can be modulated by administration of intravenous Mg2+.

Adenosine Diphosphate↗
PubMed1996

Platelet activation and coronary stent implantation. Effect of antithrombotic therapy.

BACKGROUND: Platelet activation and surface expression of adhesive glycoproteins play a key role in ischemic thrombotic complications after coronary intervention. The purpose of this case-control study was to evaluate the effects of two different antithrombotic regimens on platelet function after coronary Palmaz-Schatz stent implantation. METHODS AND RESULTS: The study group consisted of 46 "low-risk" patients who were treated with ticlopidine (250 mg BID) and aspirin (100 mg BID) after stenting. The control group was derived from a cohort of 151 patients receiving conventional anticoagulation therapy, including phenprocoumon (target international normalized ratio, 3.5), heparin (activated partial thromboplastin time, 80 to 120 seconds), and aspirin (100 mg BID) after stenting. Criteria for matching were indication for stenting, target vessel, balloon size, inflation pressure, and number of inserted stents. Matches were obtained for 38 patients. Platelet function was evaluated before and daily for 12 days after stenting in venous blood samples with immunologic activation markers. Patients receiving anticoagulation therapy showed a significantly increased surface exposure of LIBS1 (activated fibrinogen receptor; P < .05) and CD62P (P-selectin; P < .001) above prestent values, peaking days 3 to 6 after stenting. In contrast, in patients receiving ticlopidine, expression of LIBS1 decreased (P < .01) and expression of CD62P remained basically unchanged after stenting. Platelet count significantly decreased after stenting in patients treated by anticoagulation (day 3; P < .01), whereas no significant changes were found in the ticlopidine group. CONCLUSIONS: Significant platelet activation occurs in patients receiving anticoagulation therapy after stenting, while platelet deactivation is found in patients treated with combined antiplatelet therapy. This may contribute to a lowering of the incidence of subacute stent thrombosis.

Adult↗
PubMed1996

Neutrophil and platelet activation at balloon-injured coronary artery plaque in patients undergoing angioplasty.

OBJECTIVES: This study sought to investigate changes in the expression of activation-dependent adhesion receptors on neutrophils and platelets after exposure to the balloon-injured coronary artery plaque. BACKGROUND: Activation of blood cells at the balloon-injured coronary artery plaque may contribute to abrupt vessel closure and late restenosis after percutaneous transluminal coronary angioplasty. METHODS: In 30 patients undergoing elective coronary angioplasty, blood specimens were obtained through the balloon catheter proximal to the plaque before dilation and distal to the plaque after dilation. Simultaneous blood samples obtained through the guiding catheter served as control samples. Total surface expression of the inducible fibrinogen receptor (CD41) and surface expression of the activated fibrinogen receptor (LIBS1) on platelets as well as Mac-1 (CD11b) and L-selectin (CD62L) surface expression on neutrophils were assessed by flow cytometry. RESULTS: After exposure to the dilated coronary artery plaque, surface expression of LIBS1 on platelets increased by 40.5 +/- 11.0 mean (+/-SE) fluorescence (p=0.001) and that of CD11b on neutrophils increased by 20.1 +/- 4.4 mean fluorescence (p=0.018). Concomitantly, anti-CD62L binding on neutrophils decreased by 6.6 +/- 2.4 mean fluorescence (p=0.022). In contrast, surface expression of the adhesion receptors did not change significantly between the coronary ostium and the prestenotic coronary segment. CONCLUSIONS: The results of this study demonstrate neutrophil and platelet activation at the balloon-injured coronary artery plaque. This cellular activation may serve as a target for pharmacologic interventions to improve the outcome of coronary angioplasty.

Adult↗
PubMed1996

Platelet function in acute myocardial infarction treated with direct angioplasty.

BACKGROUND: In acute myocardial infarction (AMI), platelets play a key role in thrombotic processes that limit the patency of the recanalized, infarct-related coronary artery and contribute to reperfusion injury. Platelet function in the course of AMI treated by direct percutaneous transluminal coronary angioplasty (PTCA) has not been evaluated. METHODS AND RESULTS: In 15 patients with anterior AMI, peripheral venous blood samples were obtained before and 4, 8, 24, and 48 hours after recanalization of the occluded artery by PTCA. Fifteen patients who had stable coronary heart disease and were undergoing elective balloon angioplasty served as control subjects. Fibrinogen receptor function and surface expression of P-selectin on platelets were determined by flow cytometry. In addition, we evaluated generation of platelet-derived microparticles and the effect of systemic plasma from patients with AMI on normal platelet function and on platelet adhesion to human endothelial cells in culture. We found fibrinogen receptor activity and P-selectin expression on circulating platelets 8 hours after direct PTCA are decreased (P < .01). This coincided with a decrease in peripheral platelet count (P < .05) and an increase in generation of microparticles (P < .002). Twenty-four to 48 hours after PTCA, fibrinogen receptor activity and P-selectin expression increased again. Systemic plasma obtained before and after direct PTCA sensitized normal platelets to hyperaggregate in vitro (P < .001) and stimulated platelet adhesion to endothelial cells in culture (P < .01). None of the changes found in AMI were detectable in the control group. CONCLUSIONS: After transient apparent deactivation of circulating platelet, probably caused by sequestration of hyperactive platelets, the level of platelet activation increases in patients with AMI treated by direct PTCA. These findings underscore the need for novel antiplatelet strategies in AMI.

Adult↗
PubMed1996

Prospective evaluation of hemostatic predictors of subacute stent thrombosis after coronary Palmaz-Schatz stenting.

OBJECTIVES: This study sought to investigate hemostatic predictors of subacute occlusive coronary stent thrombosis. BACKGROUND: Better hemostatic monitoring may improve antithrombotic therapy after stenting. METHODS: In 140 consecutive patients undergoing Palmaz-Schatz stent implantation for suboptimal angioplasty results, we obtained serial blood samples immediately before and daily for 12 days after stenting. We prospectively tested the hypothesis that subacute stent thrombosis was more frequent if the surface expression of the inducible fibrinogen receptor on platelets (flow cytometry) or the concentration of plasma fibrinogen or that of the prothrombin fragments F1 + 2 before stent implantation exceeded the 75th percentile of the entire study cohort. RESULTS: All five stent occlusions encountered during the study occurred in patients with platelet fibrinogen receptor expression above the 75th percentile. Thus, the rate of stent occlusion differed significantly between the groups defined by platelet fibrinogen receptor expression (14.3% vs. 0%, p = 0.0008). In both the group with fibrinogen concentration and that with F1 + 2 concentration above the 75th percentile, three stent occlusions occurred. Between the groups defined by these variables, the rate of stent occlusion did not differ significantly (8.6% vs. 1.9%, p = 0.10). Logistic regression analysis, including angiographic and hemostatic variables, confirmed platelet fibrinogen receptor expression as an independent predictor of stent occlusion (p = 0.020). Stent occlusion could not be predicted by the time course of any of the hemostatic variables. CONCLUSIONS: Platelet fibrinogen receptor expression is an independent predictor of subacute stent occlusion. However, fibrinogen and F1 + 2 concentrations do not show a strong relation to the risk of stent occlusion.

Adult↗
PubMed1996

Immunoreactivity of glycoprotein IIb is present in metastasized but not in non-metastasized primary malignant melanoma.

Glycoprotein IIb-IIIa (integrin alpha IIb beta3) is an adhesive receptor involved in platelet aggregation and adhesion to the extracellular matrix. Previous studies showed the presence of IIb-IIIa-like glycoproteins on cells of melanoma cell lines and on cells of lymph node metastases. This study evaluates the presence of glycoprotein IIb-IIIa subunits on cells of primary cutaneous malignant melanomas with (n = 4) and without (n = 9) metastases over a period of 6 years and on naevus cells (n = 4). Monoclonal antibodies directed against the subunits of the glycoprotein IIb-IIIa receptor were used on paraffin-embedded sections and evaluated by means of immunohistochemistry. The glycoprotein IIb subunit was exclusively present on cells of metastatic melanomas. It was not found on non-metastatic melanomas or benign melanocytes. These data favour the role of the integrin receptor glycoprotein IIb-IIIa in the metastatic behaviour of malignant melanomas.

Adult↗
PubMed1996

Changes in membrane glycoproteins of circulating platelets after coronary stent implantation.

OBJECTIVES: To evaluate platelet function in patients with coronary stents. DESIGN: A non-randomised control trial in 30 patients who had immediate implantation of Palmaz-Schatz coronary stents because of a suboptimal angioplasty result. All patients received a standardised anticoagulation regimen including intravenous heparin (activated partial thromboplastin time (APTT) 80 to 120 s), oral vitamin K antagonist (target international normalised ratio (INR) of 3.5), and 100 mg aspirin twice daily. Platelet surface expression of glycoprotein IIb-IIIa, activated fibrinogen receptor, and P-selectin as well as binding of von Willebrand factor and fibrinogen were determined by flow cytometry in peripheral venous blood samples collected before the intervention and then daily for 4 days after it. The results were compared with those in 30 patients undergoing elective coronary balloon angioplasty. SETTING: University hospital. RESULTS: After coronary stenting surface expression of the activated fibrinogen receptor significantly increased, peaking at day 2 (P < 0.001). Similar results were found for von Willebrand factor binding and P-selectin surface expression, with a maximum at day 2 to 4 after stenting (von Willebrand factor, P < 0.001; P-selectin, P < 0.001). The changes in platelet membrane glycoproteins coincided with a significant drop in peripheral platelet count after stent placement (P < 0.01). No significant change in fibrinogen receptor activity, von Willebrand factor binding, P-selectin surface expression, or platelet count was seen in the control group. CONCLUSIONS: The present study shows that current anticoagulation treatment is inefficient in suppressing platelet activation in patients with coronary stents and, therefore, might not be the best treatment for reducing the incidence of subacute stent thrombosis.

Adult↗
PubMed1996

Agglutination of isolated platelet membranes.

Platelet membrane glycoproteins play a central role in platelet aggregation and thus in primary hemostasis. To investigate mechanisms of platelet-platelet interaction in the absence of cellular activation events, we studied immunological and functional aspects of isolated platelet membranes. Platelet membranes contained significant amounts of the inducible fibrinogen receptor, glycoprotein (GP) IIb-IIIa, which exposes conformation-dependent LIBS1 and PMI-1 epitopes in response to fibrinogen-mimetic peptides GRGDSP and HHLG-GAKQAGDV. In the presence of soluble fibrinogen, membrane-coated latex beads showed Ca(2+)-dependent agglutination that could be partially inhibited by GRGDSP but not by the biologically inactive peptide GRGESP. Thrombospondin enhanced agglutination of membrane-coated beads, which could be inhibited by polyvalent anti-thrombospondin Fab fragments and anti-thrombospondin monoclonal antibody MA-II. Mg2+ inhibited both GPIIb-IIIa- and thrombospondin-mediated agglutination of membranes in a dose-dependent manner. The results of the present study indicate that isolated platelet membranes are a useful tool to study regulation of GPIIb-IIIa- and thrombospondin-mediated platelet-platelet interaction.

Agglutination↗
PubMed1995

Cardiac release of cytokines and inflammatory responses in acute myocardial infarction.

BACKGROUND: In animal models of myocardial infarction (MI), inflammatory responses compromise microcirculation during reperfusion and restrict functional recovery. To investigate cardiac inflammatory responses in patients with acute MI, we examined the cardiac release of cytokines, the expression on neutrophils of the beta 2-integrin Mac-1 (CD11b/CD18) and L-selectin (CD62L), and the cardiac release of thrombomodulin as a marker of endothelial injury. METHODS AND RESULTS: In 12 patients with acute anterior MI, blood samples were obtained from the coronary sinus and from the aorta immediately before and after recanalization of the coronary occlusion by balloon angioplasty. Twelve patients undergoing elective balloon angioplasty served as control subjects. Plasma concentrations of interleukin (IL)-1 beta, IL-6, IL-8, tumor necrosis factor-alpha, and thrombomodulin were determined by immunoassay, and surface expression of CD11b and CD62L was assessed by flow cytometry. Differences in coronary sinus and arterial blood were found in IL-6 before (median, 6.3 ng/L, P = .01) and after (13.4 ng/L, P = .002) recanalization and in IL-8 after recanalization (10.7 ng/L, P = .02). The cardiac release of both cytokines significantly (P < or = .03) increased with reperfusion. Cytokine release after reperfusion was associated with significant transcardiac gradients in surface expression on neutrophils of CD11b (10.1 mean channel of fluorescence intensity [mean fl], P = .01) and CD62L (-87 mean fl, P = .007) and with a thrombomodulin release (4.5 micrograms/L, P = .004). Transcardiac gradients in IL-1 beta and tumor necrosis factor-alpha were not found. None of the changes found in MI were detectable in the control group. CONCLUSIONS: As evidence of cardiac inflammatory responses in reperfused acute MI, the study demonstrates cardiac neutrophil activation with signs of endothelial injury and a release of the proinflammatory cytokines IL-8 and IL-6. These findings may assist in the design of pharmacological interventions aimed at reducing microvascular reperfusion injury.

Adult↗
PubMed1995

Platelet activation and interaction with leucocytes in patients with sepsis or multiple organ failure.

This study focuses on the role of platelet membrane glycoproteins and platelet-leucocyte adhesion in patients with sepsis and multiple organ failure (MOF). Specifically, the study raises the following issues: (1) the influence of sepsis and MOF on platelet activation as assessed by surface expression of platelet membrane glycoproteins GPIIb-IIIa and thrombospondin; and (2) the effect of sepsis and MOF on platelet adhesion to circulating leucocytes. In addition, platelet activation and platelet-leucocyte adhesion are evaluated according to clinical outcome. Forty-five patients with suspected sepsis or MOF were evaluated by intensive care scoring systems (APACHE II and Elebute) to assess severity of disease. Flow cytometric techniques were used to examine platelet membrane expression of various adhesion molecules on circulating platelets and the appearance of platelet specific antigen (CD41) on leucocytes as an index of platelet-leucocyte adhesion. The results were compared with severity of disease and according to outcome in patients. Twenty-eight patients of the total study population were septic and 17 were non-septic. Twenty-two of the 28 septic patients suffered from severe MOF (APACHE II > or = 20) whereas in six septic patients MOF was absent. Eleven of the non-septic group suffered from moderate MOF whereas in six, severe MOF was present. In septic patients fibrinogen receptor activity on platelets was significantly above normal values (P < 0.001). When MOF was present, thrombospondin surface expression on circulating platelets also increased significantly (P < 0.05). Concomitantly, platelet-leucocyte adhesion was increased in sepsis (P < 0.05) and decreased in patients with MOF (P < 0.05). Significant lower levels of circulating platelet-leucocyte aggregates occurred in non-survivors (P < 0.05). We conclude that sepsis is associated with increased surface expression of platelet adhesion molecules and an increased occurrence of circulating platelet-leucocyte aggregates. The decrease in circulating platelet-leucocyte peripheral sequestration. An increased platelet-leucocyte adhesion and sequestration might account for development of MOF in the course of sepsis.

Adolescent↗
PubMed1994

Changes in platelet membrane glycoproteins and platelet-leukocyte interaction during hemodialysis.

Platelet aggregation and interaction with other vascular cells play a key role in hemostatic events during hemodialysis. We studied seven patients with end-stage renal failure on long-term hemodialysis treatment. Flow-cytometric techniques and platelet-specific monoclonal antibodies were used to measure the platelet surface expression of glycoproteins-fibrinogen receptor on glycoprotein IIb-IIIa (GP IIb-IIIa; CD41) and alpha-granule membrane protein (GMP-140; CD62). In addition, adhesion of platelets or platelet microparticles with leukocytes was evaluated by appearance of the platelet-specific antigen (GP IIb-IIIa) on leukocytes. Blood samples were taken before the start of dialysis and 15, 60, and 240 min thereafter. There was a significant increase in fibrinogen receptor activation on circulating platelets after 15 min of dialysis treatment (P < 0.001) and enhanced degranulation of GMP-140 (P < 0.05). In parallel, the interaction of platelets with neutrophils and monocytes also increased with the duration of dialysis and was maximal after 15 min (P < 0.001). We conclude that the platelet fibrinogen receptor on GP IIb-IIIa in circulating platelets is activated during hemodialysis and is associated with increased adhesion of platelets or platelet microparticles with circulating leukocytes. Thus, the phenomenon described here of platelet-leukocyte interaction could be pathophysiologically important for the development of dialysis-associated leukopenia.

Adult↗
PubMed1994

Effects of magnesium on platelet aggregation and adhesion. Magnesium modulates surface expression of glycoproteins on platelets in vitro and ex vivo.

Magnesium deficiency and its association with platelet hyperreactivity has been well recognised in a variety of diseases including myocardial infarction, preeclampsia, and diabetes. In order to investigate potential effects of intravenous Mg2+ supplementation, platelet function was studied by measurements of in vitro bleeding time (BT) and of fibrinogen (Fg)-mediated aggregation of washed platelets. In addition, the effect of Mg2+ on platelet adhesion onto immobilised Fg, on Fg binding to activated platelets, and on surface expression of GMP-140 or GP53 was evaluated. Mg2+ (4 mM) prolonged in vitro BT by 30% and inhibited Fg-mediated aggregation significantly, independent of the agonist used to initiate platelet aggregation (ADP, collagen, epinephrine, thrombin, phorbol ester). Adhesion of resting platelets to immobilised Fg was reduced by 50% in the presence of 2 mM Mg2+. Moreover, Mg2+ reduced Fg binding to ADP- or collagen-stimulated platelets as well as surface expression of GMP-140 with an IC50 of approximately 3 mM. Intravenous administration of Mg2+ to healthy volunteers inhibited both ADP-induced platelet aggregation (p < 0.05) by 40% and binding of Fg or surface expression of GMP-140 by 30% (p < 0.05). Thus, pharmacological concentrations of Mg2+ effectively inhibit platelet function in vitro and ex vivo.

Bleeding Time↗
PubMed1994

[Quality control of stored platelet concentrates by means of flow cytometry].

Storage of single-donor platelets is currently limited to 5 days. During this period, however, numerous morphologic and biochemical changes have been observed. The present study describes increased binding of anti-GMP 140 to stored single-donor platelet concentrates; this reveals a progressive activation process. In contrast, when stored platelets are stimulated with ADP, GMP 140, expression is reduced indicating a diminished release reaction. Additionally, the GP IIb/IIIa receptor complex and its fibrinogen-induced binding site (LIBS1) are reduced by storage time, demonstrating a diminished fibrinogen binding. Further experiments have to clarify whether these changes observed in vitro translate into a reduced hemostatic capacity after transfusion in vivo.

Blood Donors↗
PubMed1992

Photoaffinity labeling of integrin alpha IIb beta 3 (glycoprotein IIb-IIIa) on intact platelets with 8-azido-[gamma-32P]ATP.

The fibrinogen receptor GPIIb-IIIa plays a crucial role in platelet aggregation. Here we show that the adenine nucleotide, 8-azido-ATP, inhibits ADP-induced conformational change of the platelet fibrinogen receptor GPIIb-IIIa (integrin alpha IIb beta 3). Photoaffinity labeling of intact platelets with 8-azido-[gamma-32P]ATP exclusively modifies two plasma-membrane glycoproteins which are identical with both subunits of GPIIb-IIIa. The presence of adenine-nucleotide-binding sites on GPIIb-IIIa implies that the platelet fibrinogen receptor is directly regulated by extracellular adenine nucleotides.

Adenosine Diphosphate↗
PubMed1990

Structure-function studies of adenine nucleotide transport in mitochondria. I. Construction and genetic analysis of yeast mutants encoding the ADP/ATP carrier protein of mitochondria.

The gene encoding the major ADP/ATP carrier in yeast AAC2 (pet9; Lawson, J., and Douglas, M. (1988) J. Biol. Chem. 263, 14812-14818) has been disrupted (delta AAC2) by itself and in combination with a disruption of a second translocator gene AAC1 (delta AAC1). Disruption of AAC2 like the pet9 mutation renders yeast unable to grow on a nonfermentable carbon source. The AAC1 AAC2 double disruption exhibits a phenotype identical to the AAC2. This provides the host strain for the analysis of point mutations in the AAC protein. We have initiated this structure-function analysis by characterizing and confirming that the pet9 mutation is a G to A transition resulting in an arginine to histidine change at position 96. Site-directed replacements at Arg96 confirm its essential function for growth on a nonfermentable carbon source. These data also suggest that in the absence of functional AAC1 and AAC2 gene products, adenine nucleotide transport across the mitochondrial inner membrane must occur by an as yet unidentified translocator or translocation mechanism or that within these cells separate intra- and extramitochondrial adenine nucleotide pools can exist to support growth.

Amino Acid Sequence↗