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R M Mesters

Publications and source records attributed to R M Mesters.

29 records · Page 2Linked to original sources
PubMed1997

Comparative analysis of plasminogen activator inhibitor-1 expression in different types of atherosclerotic lesions in coronary arteries from human heart explants.

OBJECTIVES: Clinical manifestations of coronary heart disease result primarily from the progressive development of atherosclerotic plaques and subsequent thrombus formation: processes which may be accelerated by an enhanced expression of plasminogen activator inhibitor (PAI-1) in the vessel wall. In the present study, content and expression of PAI-1 were comparatively analyzed in human coronary arteries in relation to the presence and severity of atherosclerotic lesions. METHODS: Segments of coronary arteries obtained from heart explants (n = 15) were classified by the presence and types of atherosclerotic lesions. Antigen and activity levels of PAI-1 were determined in protein extracts of intimal and medial layers. In situ hybridization and immunohistochemical analyses were performed on serial sections of representative tissue specimens. RESULTS: Total PAI-1 antigen consistently increased from macroscopically normal areas (MNAs) to early lesions (ELs) and to maximal levels in fibrous (FPs) and calcified (CPs) plaques. No PAI activity was detected, although PAI-1 in its free form was present in all vascular specimens. Both free PAI-1 and PAI-1 complexed with plasminogen activators were significantly increased in extracts of advanced lesions. However, there was a 2-3 fold molar excess of free versus complexed PAI-1 in FPs and CPs. These findings suggest the presence of relevant amounts of PAI-1 in its substrate rather than in its inhibitor conformation in areas of advanced lesions. Compared with MNAs, PAI-1 mRNA was strongly expressed within the thickened intima of ELs. The highest PAI-1 expression was observed in FPs and CPs, being mainly localized in areas surrounding the necrotic cores in co-localization with infiltrating macrophages. CONCLUSIONS: PAI-1 content is consistently increased in relation to the severity of the lesions in atherosclerotic coronary arteries. The concomitant elevation of PAI-1 mRNA suggests that the PAI-1 increase in regulated by local synthesis in the areas of atherosclerotic lesions.

Antigens↗
PubMed1997

Reciprocal changes in circulating interleukin-6 and its soluble receptor during evolving sepsis in leukocytopenic patients.

Plasma concentrations of interleukin-6 (IL-6) and its soluble receptor (sIL-6R) were serially determined in 32 patients with acute myeloid leukemia who developed severe sepsis (n = 19) or septic shock (n = 13) during chemotherapy-induced leukocytopenia (< or = 1 x 10(9)/L). Starting within 2 h of fever onset, IL-6 levels rose significantly over baseline in both groups to markedly higher levels in patients with evolving septic shock (medians: 372 vs. 3671 pg/mL; P < .001). Simultaneously, sIL-6R significantly decreased to lower levels in shock patients than in septic patients without hypotension (53 vs. 93 ng/mL; P = .02). This pattern was maintained throughout the observation period of up to 6 days. In patients with fatal sepsis, peak IL-6 levels were significantly higher than in survivors (P < .001), whereas minimum sIL-6R levels were markedly lower (P = .003). The reciprocal changes in circulating IL-6 and sIL-6R suggest a role for sIL-6R in modulating the effects of IL-6 during evolving sepsis in leukocytopenic patients.

Acute Disease↗
PubMed1996

Factor VIIa and antithrombin III activity during severe sepsis and septic shock in neutropenic patients.

Septic shock and multiple organ failure may be associated with coagulation activation, disseminated fibrin formation, and consumption of coagulation inhibitors such as antithrombin III. We have evaluated prospectively coagulation measurements in patients with severe chemotherapy-induced neutropenia. This group of patients was chosen because of their high risk of developing severe septic complications, thus allowing serial prospective coagulation testing before and during evolving sepsis or septic shock. Sixty-two patients with febrile infectious events were accrued to the study. Of these, 13 patients progressed to severe sepsis and 13 additional patients to septic shock as defined according to standard diagnostic criteria. At the onset of fever, factor (F) VIIa activity, FVII antigen and antithrombin III (AT III) activity decreased from normal baseline levels and were significantly lower in the group of patients who progressed to septic shock compared with those that developed severe sepsis (medians: 0.3 v 1.4 ng/mL, 21 v 86 U/dL and 45% v 95%; P < .001). The decrease of these measurements in septic shock was accompanied by an increase in prothrombin fragment 1+2 (median: 3.6 v 1.4 nmol/L; P = .05), a marker of thrombin generation. These differences were sustained throughout the septic episode (P < .0001). FVIIa and AT III levels of < 0.8 ng/mL and < 70%, respectively, at onset of fever predicted a lethal outcome with a sensitivity of 100% and 85%, and a specificity of 75% and 85%, respectively. In contrast, FXIIa-alpha antigen levels were not different between groups at onset of fever but increased modestly during the course of septic shock (P = .001). Thus, septic shock in neutropenic patients is associated with increased thrombin generation. Furthermore, both FVIIa and AT III measurements are sensitive markers of an unfavorable prognosis.

Adult↗
PubMed1996

Increase of plasminogen activator inhibitor levels predicts outcome of leukocytopenic patients with sepsis.

Variables of the fibrinolytic system were prospectively studied in patients with haematologic malignancies in chemotherapy-induced leukocytopenia at onset and during the course of septicemia to evaluate their prognostic value. This group of patients was chosen because of their high risk of developing severe septic complications, thus allowing serial prospective testing of fibrinolytic variables prior to and during evolving sepsis or septic shock. 62 patients with febrile infectious events were accrued to the study. Of these, 13 patients progressed to severe sepsis and an additional 13 patients to septic shock as defined according to standard diagnostic criteria. At onset of fever, plasminogen activator inhibitor (PAI) activity and PAI-1 antigen levels increased from normal baseline levels and were significantly higher in the group of patients who developed septic shock compared to those with severe sepsis (medians: 10.6 versus 1.3 U/ml, p = 0.0001; 50.0 versus 5.0 ng/ml, p = 0.0002). The increase in PAI activity and antigen in septic shock was accompanied by an increase in tissue-type plasminogen activator antigen and total fibrin(ogen) degradation products and a decrease in alpha(2)-antiplasmin activity (p < 0.006). In contrast, in the group of patients that developed severe sepsis the variables of the fibrinolytic system remained unchanged at onset of fever. These differences between septic shock and severe sepsis were sustained throughout the septic episode for all variables (p < 0.0001). PAI activity of > 5 U/ml at onset of fever predicted a lethal outcome with a sensitivity of 92% and a specificity of 100%. Thus, septic shock in leukocytopenia is associated with significant activation of the fibrinolytic system presumably as a response of the vascular endothelium to inflammatory injury. Furthermore, PAI activity measurements are sensitive markers of an unfavourable prognosis.

Adult↗
PubMed1995

Markers of coagulation activation for evaluation of the antithrombotic efficacy of heparin: a prospective study in acute deep venous thrombosis.

The potential value of measurements of prothrombin fragment 1 + 2 (F1 + 2), thrombin-antithrombin complexes (TAT) and D-dimer for the assessment of antithrombotic efficacy of heparin in acute deep venous thrombosis (DVT) was prospectively investigated. These variables were determined at presentation and subsequently once daily during a course of seven days heparin therapy. Heparin doses were adjusted according to the activated partial thromboplastin time (APTT). Compression ultrasonography was performed at presentation and on day 7 to determine the extent of thrombosis according to a predefined score. Out of a total of 50 patients accrued to the study 44 patients had reduced or unchanged extent of thrombosis, whereas in six patients an extension was documented. Although thrombin generation was significantly inhibited after initiation of heparin therapy as reflected by a decrease in F1 + 2 and TAT levels, these markers were not useful for the detection of patients with DVT extension. In contrast, anti-factor-Xa activities but not APTT measurements were significantly lower in the group of patients with propagation of DVT (median: 0.22 U/ml versus 0.38 U/ml, interquartile range: 0.1-0.33 U/ml versus 0.19-0.55 U/ml; P = 0.001). D-dimer decreased within the first days of heparin therapy but failed to indicate DVT progression. These data suggest that plasma anti-factor-Xa activity correlates better with the antithrombotic efficacy of heparin than APTT measurements and markers of coagulation or fibrinolysis activation.

Adult↗
PubMed1994

Cytokine response to infection in patients with acute myelogenous leukaemia following intensive chemotherapy.

Septic shock is the major cause of treatment-related death in patients with acute myelogenous leukaemia (AML) undergoing intensive chemotherapy. Interleukins (IL)-1 beta, -6, -8, and tumour necrosis factor alpha (TNF-alpha) have been implicated as mediators of septic shock, with circulating leucocytes being considered a major source for their release. However, plasma cytokine levels of leucocytopenic patients with evolving sepsis have not been studied. We have prospectively measured plasma cytokines during chemotherapy-induced leucocytopenia (< 1 x 10(9)/l) in 50 patients with AML. Cytokine levels in patients with severe sepsis (n = 5) or septic shock (n = 8) were compared to those measured in 13 matched patients with uncomplicated febrile infections. In evolving septic shock, IL-6, IL-8 and TNF-alpha peaked within 48 h of fever onset at levels reported for non-leucocytopenic patients and distinctively higher than during uncomplicated febrile episodes (P < 0.05). Peak concentrations measured within 48 h after onset of fever were related to fatal outcome. IL-1 beta was detected in less than 5% of all samples. Cytokine concentrations were unrelated to leucocyte counts and markers of neutrophil or monocyte activation (elastase and neopterin levels, respectively). We conclude that cytokine release associated with evolving septic shock in patients with AML does not depend on circulating leucocytes.

Adult↗
PubMed1993

A novel exosite in the light chain of human activated protein C essential for interaction with blood coagulation factor Va.

Activated protein C (APC) exerts its physiologic anticoagulant role by proteolytic inactivation of the blood coagulation cofactors Va and VIIIa. To identify regions on the surface of the light chain of APC that mediate anticoagulant activity, 10 synthetic peptides were prepared and tested for their ability to inhibit APC anticoagulant activity. The synthetic peptide-(142-155) inhibited APC anticoagulant activity in Xa-1-stage coagulation assays in normal and protein S-depleted plasma with 50% inhibition at 5-25 microM peptide. In a system using purified clotting factors, peptide-(142-155) inhibited APC catalyzed inactivation of factor Va in the presence or absence of phospholipids with 50% inhibition at 50 microM peptide. However, peptide-(142-155) had no effect on APC amidolytic activity or on the reaction of APC with the serpin, recombinant [Arg358]-alpha 1-antitrypsin. Moreover, peptide-(142-155) inhibited factor Xa clotting activity in normal plasma as well as in a prothrombinase assay in the presence of factor Va with 50% inhibition at 5 microM and 50 microM peptide, respectively, under the assay conditions. The peptide had no significant effect on factor Xa or thrombin amidolytic activity and no effect on the clotting of purified fibrinogen by thrombin, suggesting that it does not directly inhibit these enzymes' active sites. Peptide-(142-155) was shown to bind directly to immobilized factor Va.(ABSTRACT TRUNCATED AT 250 WORDS)

Amides↗
PubMed1993

Binding of protein S to factor Va associated with inhibition of prothrombinase that is independent of activated protein C.

Since plasma protein S serves an anticoagulant function by mechanisms which are not completely understood, its possible interaction with Factor Va was investigated. Human protein S bound to immobilized human Factor Va in a calcium-dependent, saturable, and reversible manner and Factor Va bound similarly to immobilized protein S. Binding of protein S to immobilized Factor V was greatly enhanced by pretreatment of the surface-bound Factor V with increasing doses of thrombin up to 1 unit/ml. Binding of protein S to Factor Va was also demonstrated in fluid phase with a Kd of 33 +/- 9 nM. Biotin-labeled heavy chain of Factor Va bound to immobilized protein S, and this binding was reversed by a 17-fold molar excess of intact unlabeled Factor Va. Protein S competed efficiently with prothrombin for binding to immobilized Factor Va. The prothrombinase activity in a reaction mixture of purified clotting factors was inhibited by protein S and exhibited a pattern of mixed inhibition. The concentration of protein S needed for 50% inhibition of the prothrombinase activity of a mixture containing 1 nM Factor Xa, 20 pM Factor Va, and 50 microM phospholipids was about 16 nM. Since not all protein S preparations exhibited this degree of prothrombinase inhibitory activity, extensive control experiments were performed to verify that the inhibitory activity was associated with protein S during immunoaffinity chromatography and was not caused by traces of activated protein C in the protein S preparations. These data show that protein S has an anticoagulant function which is independent of activated protein C and, at least in part, that this is because of its competition with prothrombin for direct binding to Factor Va.

Binding, Competitive↗
PubMed1993

Interactions and inhibition of blood coagulation factor Va involving residues 311-325 of activated protein C.

Activated protein C (APC) exerts its physiologic anticoagulant role by proteolytic inactivation of the blood coagulation cofactors Va and VIIIa. The synthetic peptide-(311-325) (KRNRTFVLNFIKIPV), derived from the heavy chain sequence of APC, potently inhibited APC anticoagulant activity in activated partial thromboplastin time (APTT) and Xa-1-stage coagulation assays in normal and in protein S-depleted plasma with 50% inhibition at 13 microM peptide. In a system using purified clotting factors, peptide-(311-325) inhibited APC-catalyzed inactivation of factor Va in the presence or absence of phospholipids with 50% inhibition at 6 microM peptide. However, peptide-(311-325) had no effect on APC amidolytic activity or on the reaction of APC with the serpin, recombinant [Arg358]alpha 1-antitrypsin. Peptide-(311-325) surprisingly inhibited factor Xa clotting activity in normal plasma, and in a purified system it inhibited prothrombinase activity in the presence but not in the absence of factor Va with 50% inhibition at 8 microM peptide. The peptide had no significant effect on factor Xa or thrombin amidolytic activity and no effect on the clotting of purified fibrinogen by thrombin, suggesting it does not directly inhibit these enzymes. Factor Va bound in a dose-dependent manner to immobilized peptide-(311-325). Peptide-(311-315) inhibited the binding of factor Va to immobilized APC or factor Xa.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Identification of a sequence of human activated protein C (residues 390-404) essential for its anticoagulant activity.

Activated protein C (APC) exerts its physiologic anticoagulant role by proteolytic inactivation of the blood coagulation cofactors Va and VIIIa. To identify the regions on the surface that mediate anticoagulant activity, 26 synthetic peptides were prepared representing 90% of the human protein C heavy chain primary structure and tested for their ability to inhibit APC anticoagulant activity. Peptide-(390-404) specifically inhibited APC activity in activated partial thromboplastin time and Xa-1-stage coagulation assays in normal, in protein S-depleted and Factor VIII-deficient plasma with 50% inhibition at 5 microM peptide. Polyclonal antibodies raised against this peptide and immunoaffinity-purified on a protein C-Sepharose column inhibited APC anticoagulant activity in activated partial thromboplastin time and Xa-1-stage assays in normal, protein S-depleted, and Factor VIII-deficient plasma with half-maximal inhibition at 30 nM anti-(390-404) antibody. Neither the peptide-(390-404) nor the anti-(390-404) antibodies inhibited APC amidolytic activity or the reaction of APC with recombinant [Arg358] alpha 1-antitrypsin. Furthermore, in a purified system, peptide-(390-404) inhibited APC-catalyzed inactivation of Factor Va in the presence as well as in the absence of phospholipids with 50% inhibition at 4 microM peptide. These data suggest that the region containing residues 390-404 in APC is essential for anticoagulant activity and is available to interact with antibodies or with other proteins such as the macromolecular substrates Factors Va or VIIIa.

Amino Acid Sequence↗