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Biomedical subjects

W Muntean

Publications and source records attributed to W Muntean.

At least 55 records · Page 3Linked to original sources
PubMed1997

Activation of the clotting system: heparin-coated versus non coated systems for extracorporeal circulation.

UNLABELLED: The purpose of this experimental study was to compare heparin-coated versus non-coated systems for extracorporeal membrane oxygenation (ECMO), to investigate the dynamic course of clotting activation in both groups. METHODS: Eight pigs weighing 19.7 (+/- 1.3) kg, each underwent ECMO for 24 hours. Two groups were formed: in group 1, heparin-coated circuits were used with low dose heparinization (10 IU/kg/hr), whereas in group 2 non-coated circuits with high dose heparinization (60 IU/kg/hr) were used. Coagulation was monitored by measuring prothrombin time, partial thromboplastin time, fibrinogen, antithrombin III (AT III) and specific markers of clotting activation (thrombin-antithrombin III complexes (TAT) and D-dimer). Furthermore, platelet count, hematocrit, activated clotting time (ACT), and plasma heparin concentration were determined regularly RESULTS: The dynamic course of the specific coagulation activation markers showed some differences: whereas TAT and D-dimer increased quickly in group 2, the increase in group 1 was delayed. Activation marker values tended to be lower in group 1 during the first six hours, after which no more differences between the groups were seen. After 24 hours of ECMO, TAT and D-dimer had nearly returned to baseline values. Platelets showed a continuous decrease throughout the experiment, which was very similar in both groups. CONCLUSIONS: The heparin coated system showed a distinct delay in clotting activation during the first six hours of ECMO. After six hours there were no more differences between the groups.

Animals↗
PubMed1996

Flow cytometric detection of intracellular platelet antigens.

Exocytosis following platelet activation leads to translocation of CD62P (P-selectin), CD63, and thrombospondin from cytoplasmic granules to the cell surface membrane, where these molecules, serving as activation markers, can be detected by flow cytometry. We report the detectability of these molecules preformed--prior to platelet activation--inside the cytoplasm of resting platelets. Two different methods are described, using either methanol or the Fix&Perm kit for cell membrane permeabilization. In addition, interleukin(IL-)1 alpha is shown to be present in platelet cytoplasm after methanol treatment but not after permeabilization using Fix&Perm. Whenever cell surface positivity for a specific marker coincides with intracellular presence, blocking of the surface membrane sites prior to membrane permeabilization is required in order to obtain fluorescence intensity attributable to cytoplasmic staining only. Our data demonstrate the feasibility of the methods described for the detection of intracellular platelet molecules.

Adult↗
PubMed1996

Method for the determination of vitamin K1(20) in human plasma by stable isotope dilution/gas chromatography/mass spectrometry.

A method for the quantitative determination of vitamin K1(20) (VK), an essential cofactor in the carboxylation of clotting factors, is presented. The assay is based on gas chromatography/electron impact mass/spectrometry. The preparation of deuterium-labelled vitamin K1(20) for use as an internal standard is described. The method involves extraction of VK from human plasma and its derivatization to the heptafluorobutyryl ester after reduction of one carbonyl group with zinc. The detection limit was found to be 1.0 pg and the limit of quantitation 2.0 pg ml-1 plasma. This permits the measurement of vitamin K1(20) even in small quantities of plasma, which is highly desirable in investigations dealing with clotting abnormalities in neonates and infants.

Calibration↗
PubMed1996

Activation of the clotting system during extracorporeal membrane oxygenation in term newborn infants.

OBJECTIVES: To determine the degree of clotting activation that occurs with the usual anticoagulation regimen with systemic heparinization. METHODS: To allow a standardized comparison of the patients, this study focused on the first 48 hours of extracorporeal membrane oxygenation (ECMO) in term newborn infants. The ECMO perfusion circuit consisted of a roller pump, silicone membrane lungs, and silicone rubber tubing. Coagulation was controlled routinely by measuring prothrombin time, fibrinogen, antithrombin III, and reptilase time. Platelet counts, activated clotting time, and heparin concentration were controlled regularly. The following specific activation markers of the clotting system were measured: prothrombin activation fragment 1 + 2(F1+2), thrombin-antithrombin III complexes, and D-dimer. Measurements were done before the start of ECMO, after 5 minutes, and at hours 1, 2, 3, 4, 6, 12, 24 and 48. RESULTS: All seven term infants had excessively high levels of clotting activation markers within the first 2 hours of ECMO: F1+2, 11.6(+/- O.9) nmol/L (mean +/- SEM); thrombin-antithrombin, 920(+/- 2.2) microg/L; D-dimer, 15.522(+/- 3.689) ng/L. During the next 46 hours of ECMO, F1+2 and thrombin-antithrombin III complexes decreased from those high values, whereas D-dimer did not. The increase of activation markers was accompanied by low fibrinogen, low platelet counts. and prolongation of reptilase time. CONCLUSIONS: These findings fit the pattern of consumptive coagulopathy during neonatal ECMO, especially in the first 24 hours.

Anticoagulants↗
PubMed1995

Serum cytokines in juvenile rheumatoid arthritis. Correlation with conventional inflammation parameters and clinical subtypes.

OBJECTIVE: To examine the usefulness of determining extended serum cytokine profiles in patients with juvenile rheumatoid arthritis (JRA), for the purpose of improving differential diagnosis and monitoring disease activity. METHODS: In a 2-year prospective study, serum levels of interleukin-1 beta (IL-1 beta), soluble IL-2 receptor (sIL-2R), IL-6, IL-8, tumor necrosis factor alpha (TNF alpha), and the p55 soluble TNF receptor (sTNFR) were repeatedly determined by enzyme-linked immunosorbent assay in 40 patients with JRA, 13 patients with postinfectious arthropathies, and 30 healthy controls. The data were compared with conventional parameters of inflammation, such as C-reactive protein (CRP), iron and hemoglobin levels, erythrocyte sedimentation rate (ESR), white blood cell (WBC) counts, and platelet counts. WBC subsets were analyzed by flow cytofluorometry. RESULTS: At the first visit and at the peak of inflammatory activity according to CRP levels and/or ESR, serum levels of sIL-2R, IL-6, and sTNFR in JRA patients correlated significantly with conventional inflammation indicators, whereas IL-1 beta, IL-8, and TNF alpha did not. No changes in leukocyte subset distribution were noted. Among the different clinical subtypes of JRA, sIL-2R, IL-6, and sTNFR values at the time of the initial visit showed a pattern similar to CRP, whereby patients with systemic disease exhibited by far the highest values. TNF alpha and IL-1 beta were variably elevated in certain JRA subtypes. Patients with postinfectious arthropathies showed elevated levels of CRP, sIL-2R, TNF alpha, and sTNFR, which did not differ significantly from levels in the various JRA subtypes with the exception of systemic disease. Detailed analysis of types I and II pauciarticular JRA revealed that levels of CRP, IL-1 beta, and TNF alpha were elevated in patients with type I disease. While these parameters were invariably normal in patients with type II disease, sTNFR and sIL-2R were still found to be significantly elevated. Followup studies suggested that persistently high sTNFR values are a better indicator of JRA activity than are measurements of other cytokines or CRP. CONCLUSION: JRA is associated with significant and consistent changes in serum levels of inflammatory cytokines and soluble receptors. For the clinical monitoring of JRA, determination of levels of sTNFR, and to some extent sIL-2R, may be particularly useful, since these determinations yield information about subtype and/or activity of disease that is not available from conventional parameters of inflammation.

Adolescent↗
PubMed1995

Inherited resistance to activated protein C in a boy with multiple thromboses in early infancy.

Resistance to activated protein C is a recently discovered genetic defect with a high prevalence in adult patients with thromboembolic disease. It is an autosomal dominant disorder and is ten times more common in these patients than antithrombin III-, protein C- and protein S deficiency together. In spite of this high prevalence among adults with thromboembolic disease no clinical manifestation in infancy so far has been reported. We describe a 4-year-old boy with a complex cardiac malformation and inherited resistance to activated protein C, who developed multiple thromboses after cardiac catheterization in early infancy. Conclusion. Resistance to activated protein C can cause thrombosis in infants and children if additional risk factors for the development of thrombosis are present.

Blood Coagulation Tests↗
PubMed1995

Effects of heparin and hirudin on thrombin generation and platelet aggregation after intrinsic activation of platelet rich plasma.

The effects of unfractionated heparin (UH) and recombinant hirudin (rH) on prothrombin activation, free thrombin generation, and platelet aggregation induced by endogenously generated thrombin after intrinsic activation of platelet rich plasma were compared. Free thrombin generation and platelet aggregation were assessed simultaneously by delaying fibrinogen polymerisation with GPRP. UH more effectively inhibited prothrombin activation and free thrombin generation than rH. Increasing concentrations of rH had hardly any effect on the peak amount of free thrombin, while in the presence of 400 nM UH only traces of free thrombin were detected. Comparison of TAT and THC (thrombin-hirudin complex) generated until the onset of platelet aggregation on a molar basis showed that much more thrombin was inactivated in the presence of rH than in plasma containing UH. The explosive generation of free thrombin in hirudinized plasmas was accompanied by a markedly steeper aggregation curve as compared to heparinized plasmas. The generation of thromboxane B2 was markedly delayed in the presence of UH but not influenced in the presence of rH. Our results suggest that UH is more effective than rH in inhibiting prothrombin activation after intrinsic activation of platelet rich plasma, while rH prevents clotting more by direct inactivation of already generated thrombin. The inability of even high concentrations of rH to prevent the explosive generation of free thrombin might contribute to the observed inefficiency of rH to inhibit platelet aggregation.

Blood Platelets↗
PubMed1994

Inhibitor to factor V after exposure to fibrin sealant during cardiac surgery in a two-year-old child.

A two-year-old infant developed an inhibitor to factor V after cardiac surgery, with application of fibrin sealant containing bovine thrombin. Investigation of this inhibitor by means of inhibition experiments and immunoblot analysis revealed that the inhibitor reacted strongly with bovine, but only weakly with human factor V. Plasmapheresis proved effective in increasing factor V levels. This patient provides further evidence that exposure to topical thrombin preparations may lead to the development of inhibitors in the postoperative period that may cause bleeding complications.

Anastomosis, Surgical↗
PubMed1994

Thrombin-Hirudin complex formation, thrombin-antithrombin III complex formation, and thrombin generation after intrinsic activation of plasma.

To investigate the relative importance of direct inhibition of thrombin by complex formation and of inhibition of thrombin generation to the mechanisms by that unfractionated heparin (UH) and recombinant hirudin (rH) exert their anticoagulant effects, thrombin-antithrombin III complex (TAT) and thrombin-hirudin complex (THC) formation was compared with the generation of thrombin and prothrombin fragments 1 + 2 (F 1 + 2). Clotting was initiated by activation of citrated plasma in the absence or presence of UH or rH using partial thromboplastin, ellagic acid and calcium chloride. THC was determined by means of ELISA using specific antibodies to thrombin and rH. Activation of citrated plasma resulted in a sudden onset of thrombin generation after a lag phase of 2 min. Addition of 50 ng rH/ml plasma or 0.1 UH/ml plasma prolonged the clotting time to 3 min. While the peak of thrombin was only slightly decreased in hirudinized plasma, in heparinized plasma thrombin generation was significantly lower than in not anticoagulated plasma. This difference was more pronounced when the lag phase was prolonged to 5 min using 400 ng rH/ml plasma or 0.35 U UH/ml plasma. Using 1200 ng rH/ml or 0.65 U UH/ml to obtain a clotting time of 9 min only a small amount of thrombin could be detected in heparinized plasma, but hirudinized plasma still showed a high peak of thrombin. F 1 + 2 showed essentially the same pattern as thrombin. Prior to the onset of visible clot formation in all experiments using different concentrations of UH about the same values of TAT were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Antithrombin III↗
PubMed1994

[Anti Ko(a) as a cause of neonatal alloimmune thrombocytopenia].

Neonatal alloimmune thrombocytopenia (NAIT) is caused by maternal immunization against a paternal antigen on fetal platelets. The antigens mostly involved are Zwa (PlA1) and Br(a). The Ko alloantigen system which is localized on the N-terminal region of glycoprotein Ib usually causes antibody formation in polytransfused patients but is only rarely implicated in NAIT. Ko(a) antibodies raised in the mother of a thrombocytopenic newborn were shown to be detectable by platelet agglutination and MAIPA assay if the antigen-bearing N-terminal glycocalicin is protected from proteolytic degradation.

Antigens, Human Platelet↗