Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.6 (thromboplastin)
13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have used organic synthesis to understand the role of L-iduronic acid conformational flexibility in the activation of antithrombin by heparin. Among known synthetic analogues of the genuine pentasaccharidic sequence representing the antithrombin binding site of heparin, we have selected as a reference compound the methylated anti-factor Xa pentasaccharide 1. As in the genuine original fragment, the single L-iduronic acid moiety of this molecule exists in water solution as an equilibrium between three conformers 1C4, 4C1 and 2S0. We have thus synthesized three analogues of 1, in which the L-iduronic acid unit is locked in one of these three fixed conformations. A covalent two atom bridge between carbon atoms two and five of L-iduronic acid was first introduced to lock the pseudorotational itinerary of the pyranoid ring around the 2S0 form. A key compound to achieve this connection was the D-glucose derivative 5 in which the H-5 hydrogen atom has been replaced by a vinyl group, which is a progenitor of the carboxylic acid. Selective manipulations of this molecule resulted in the 2S0-type pentasaccharide 23. Starting from the D-glucose derivative 28, a covalent two atom bridge was now built up between carbon atoms three and five to lock the L-iduronic acid moiety around the 1C4 chair form conformation, and the 1C4-type pentasaccharide 43 was synthesized. Finally the L-iduronic acid containing disaccharide 58 which, due to the presence of the methoxymethyl substituent at position five adopts a 4C1 conformation, was directly used to synthesize the 4C1-type pentasaccharide 61. The locked pentasaccharide 23 showed about the same activity as the reference compound 1 in an antithrombin-mediated anti-Xa assay, whereas the two pentasaccharides 43 and 61 displayed very low activity. These results clearly establish the critical importance of the 2S0 conformation of L-iduronic acid in the activation of antithrombin by heparin.
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PMID:Synthesis of conformationally locked L-iduronic acid derivatives: direct evidence for a critical role of the skew-boat 2S0 conformer in the activation of antithrombin by heparin. 1176 51

The aim of the present work was to investigate the preparation of low molecular weight heparin (LMWH) nanoparticles (NP) as potential oral heparin carriers. The NP were formulated using an ultrasound probe by water-in-oil-in-water (w/o/w) emulsification and solvent evaporation with two biodegradable polymers [poly-epsilon-caprolactone, PCL and poly(D,L-lactic-co-glycolic acid) 50/50, PLGA] and two non-biodegradable positively charged polymers (Eudragit RS and RL) used alone or in combination. The mean diameter of LMWH-loaded NP ranged from 240 to 490 nm and was dependent on the reduced viscosity of the polymeric organic solution. The surface potential of LMWH NP prepared with Eudragit polymers used alone or blended with PCL and PLGA was changed dramatically from strong positive values obtained with unloaded NP to negative values. The highest encapsulation efficiencies were observed when Eudragit polymers took part in the composition of the polymeric matrix, compared with PCL and PLGA NP exhibiting low LMWH entrapment. The in vitro LMWH release in phosphate buffer from all formulations ranged from 10 to 25% and was more important (two- to threefold) when esterase was added into the dissolution medium. The in vitro biological activity of released LMWH, determined by the anti-factor Xa activity with a chromogenic substrate, was preserved after the encapsulation process, making these NP good candidates for oral administration.
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PMID:Low molecular weight heparin-loaded polymeric nanoparticles: formulation, characterization, and release characteristics. 1245 68

Trocarin belongs to group D of prothrombin activators derived from snake venom of Tropidechis carinatus and is a rich non-hepatic source of Xa, the only known hepatic prothrombin activator. The structural and functional similarity with Xa makes trocarin an interesting target for exploring the structure-functional relationship with Xa. Herein we report a predicted complete three-dimensional all-atom structural model of trocarin equilibrated in explicit water using 4 ns of molecular dynamics simulation. The tertiary structure was modeled using the structure of human blood coagulation factor Xa. The conformational and structural features of trocarin are then compared with the X-ray crystal and solution simulation structures of human factor Xa. The modeled structure of trocarin has four individual domains (Gla, EGF1, EGF2 and SP) connected along the long axis with similar secondary structural elements to Xa. The simulations suggest that sodium ion binding in the serine protease domain is impaired in trocarin as compared to Xa. In contrast to Xa, for which the sodium ion forms an octahedral coordination network that brings two loop regions connecting four anti-parallel beta-sheets together, we do not find a similar pattern of network in trocarin. We observe that the difference in the binding pattern of sodium ion leads to a approximately 2-A "shrinkage" of the beta2 strand (B2), in comparison to human Xa, as marked by a shorter distance between 189Asp373 (S1-site residue) and 195Ser379 (active-site residue) in the B2 strand. We propose that these differences may be linked to the experimentally observed lower amidolytic activity of trocarin as compared to Xa.
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PMID:Three-dimensional solution structure of Tropidechis carinatus venom extract trocarin: a structural homologue of Xa and prothrombin activator. 1248 30

Percutaneous ultrasound-guided cholecystocentesis was performed on 13 healthy beagle dogs to determine whether percutaneous ultrasound-guided cholecystocentesis in the dog was a feasible and safe procedure. Clinical, laboratory and ultrasonographic examinations were done at 0 and 10 minutes, in the 2nd and 16th hour, and on the 7th day. They included a detailed physical examination of the mucous membranes, cardiorespiratory system and abdominal organs. Laboratory examinations of the blood consisted of a complete blood count, determination of packed cell volume (PCV), haemoglobin (Hb), total plasma protein (TPP), parameters of haemostasis including prothrombin time (PT), activated partial thromboplastin time (APTT), and enzyme activities reflecting hepatobiliary function, i.e. aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma-glutamyltransferase (GGT). Ultrasonographic findings of the gallbladder (size, shape, wall, content) and appearance of the biliary tract and the surrounding cranial intraabdominal organs were also evaluated. Percutaneous ultrasound-guided cholecystocentesis was performed easily during the study, and dogs tolerated well the procedure performed without anaesthesia. All laboratory parameters of the blood remained within normal limits throughout the study. However, some follow-up values, i.e. PCV, TPP, APTT and ALT, demonstrated statistically significant differences when compared to baseline measurements, which might reflect the effect of 24-hour fasting before the experiment, as well as day-to-day metabolic fluctuations due to feeding and water supply during the study. There were no visible signs of bleeding from the liver, bile leakage from the gallbladder or accumulation of free peritoneal fluid during repeated ultrasonographic examinations. Percutaneous ultrasound-guided cholecystocentesis seems to be an important diagnostic procedure in canine gallbladder diseases and can be used safely and easily to gain gallbladder bile for diagnosis of bacterial cholecystitis or for investigating hepatobiliary function in the dog.
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PMID:Percutaneous ultrasound-guided cholecystocentesis in dogs. 1249 44

Antenna coupling microwave plasma enables a highly oxidative treatment of the outmost surface of polypropylene (PP) nonwoven fabric within a short time period. Subsequently, grafting copolymerization with acrylic acid (AAc) makes the plasma-treated fabric durably hydrophilic and excellent in water absorbency. With high grafting density and strong water affinity, the pAAc-grafted support greatly becomes feasible as an intensive absorbent and as a support to promote heparin immobilization through amide bonds. For heparin immobilized in acidic condition, the carbonate groups of the molecule tend to dissolve and passive encapsulation of the molecule prevents its functional groups from bonding with the carboxylic acid of pAAc. This effect leads to inhibit the immobilization process and consequently reduces the quantity as well as the bioactivity of the immobilized heparin. In alkaline processing environment, the oxidized uronic acid residues in heparin-related glycans are presumably cleaved and the removal of some oxidized residuals before immobilization process is likely to reduce the chain length of heparin. In the latter case, anticoagulant Factors X and XII, but not thrombin, are unaffected. Anticoagulant activity test using activated partial thromboplastin time (aPTT) is more sensitive in assessing heparin-immobilized surfaces, since it corresponds to Factor X and initiates the inhibition of Factor XII and thrombin. Likewise, platelets adhesion on the surfaces decreases as the process shifted from acidic to alkaline condition, whereas the hydrophilic character of the grafted pAAc markedly contributes to extend physical insertion of platelets. The immobilized heparin has a great part of original bioactivity, depending on the pH of the processing environment and the immobilized quantity. Relative bioactivity based upon aPTT tests is partially held longer than 90 days for the sample prepared in the alkaline or neutral environment.
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PMID:Anticoagulant activity of immobilized heparin on the polypropylene nonwoven fabric surface depending upon the pH of processing environment. 1255

To improve the blood-compatibility of polyurethane, the co-solvent of tetrahydrofuran and water, a new solvent system for blending polyurethane and heparin, was proposed. After solvent casting, heparin was blended in a polyurethane film. The ATR-FTIR was used to analyze the surface chemical element and the contact angle was measured to investigate the hydrophilicity of the surface of the PUs. As the amount of heparin increased, the surface hydrophilicity was increased and all the clot times exceeded the measurement limit of the clot detection instrument when the heparin loaded on the polyurethane films was 3%, 5% and 7%. After the films were immersed in the phosphate buffered saline for 30 days, the activated partial thromboplastin time and thrombin time still exceeded the measurement limit of the clot detection instrument.
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PMID:A novel solvent system for blending of polyurethane and heparin. 1283 86

It has been possible to duplicate in the hemophilic dog four of the major experiments which have suggested in humans an "anticephalin" hypothesis for the pathogenesis of hemophilia. The experiments in the dog have been considerably extended, as compared with the human experiments, by a variety of techniques. I. Asbestos was placed in contact with hemophilic dog plasma, and the clotting time became shorter. When transfused, this plasma had no effect on the defective prothrombin utilization of hemophilic dogs, in contrast to untreated normal plasma. II. The ionic strength of native dog plasma and dog plasma citrated (38 per cent sodium citrate) then recalcified (0.2 M CaCl(2)) were calculated. The ionic strength of the native plasma was approximately 0.15 while that of the citrated plasma was approximately 0.21. Conductivity and freezing point determinations on the plasmas described above were consistent with the idea that the ionic strength of the citrated plasma was significantly higher. The biphasic dilution curve, to which much significance has been attached in arriving at the "anticephalin" hypothesis, can be produced readily in the dog. Diluting dog plasma with "iso-ionic" or "hyper-ionic" NaCl solution abolished the biphasic phenomenon. Dilution with distilled water exaggerated the biphasic curve. These experiments suggest that the biphasic curve is an artifact of uncontrolled ionic strength. III. The prothrombin utilization rates of undiluted whole hemophilic dog blood and hemophilic dog blood diluted 1:2 with 0.85 per cent NaCl were found to be the same. IV. Ether extraction of both normal and hemophilic dog plasma removed fibrinogen and reduced somewhat the concentration of prothrombin. In treated normal plasma AHF was reduced to the level of untreated hemophilic plasma, thus producing a quasi-hemophilic plasma. Defibrination and ether extraction of both normal and hemophilic dog plasma "generated" clotting activity which shortened the clotting time of hemophilic plasma and was active in the thromboplastin generation test. The activity "generated" by defibrination and ether extraction of dog plasma was adsorbed by a BaSO(4) suspension and shown, therefore, not to be the anti-hemophilic factor (AHF). Transfusion of ether-extracted normal or hemophilic dog plasma into hemophilic dogs had no effect on the prothrombin utilization rate, unlike untreated normal plasma which had a marked effect. Thus, four of the main lines of evidence supporting the "anticephalin" hypothesis were duplicated in the dog. However, by extending the experiments it was found that all were explainable on bases other than the presence of "anticephalin." Such an hypothesis is not necessary, therefore, to explain the pathogenesis of canine hemophilia. The apparent identity of hemophilia in the two species suggests that the hypothesis is also not applicable to humans.
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PMID:The pathogenesis of hemophilia; an experimental analysis of the anticephalin hypothesis in hemophilic dogs. 1344 37

Fondaparinux is a synthetic selective inhibitor of factor Xa recently approved for thromboprophylaxis after major orthopedic surgery. Determination of its concentration gives valuable insight into specific pharmacokinetics or safety studies. The aim of the study was to develop direct, sensitive, precise and accurate assays of fondaparinux sodium in different biological matrices. Consistency with the recommended chromogenic assay for low molecular weight heparin required a similar method. However, recent data indicated some variability in the determination of anti-Xa level between commercial chromogenic assays. Consequently, we developed and validated two chromogenic methods (A and B) for assaying fondaparinux in plasma and other biological matrices. The assays are calibrated with fondaparinux, a pure chemical entity, and the result is expressed as amount (microg) of the fondaparinux calibrator. Results showed that precision was lower than 5.2% in plasma or plasma water and 13% in placental medium. The accuracy was lower than 7.6% in plasma or plasma water and 10.2% in placental medium. The lower limit of quantification in plasma was 0.042 microg/mL with automated Method A and 0.019 microg/mL with Method B. The assay was not affected by the source of the samples, the presence of blood cells, EDTA, citrate or repeated cycles of freezing and thawing. The two chromogenic assays calibrated with fondaparinux sodium reach the equivalence criteria for plasma samples and provide reliable and reproducible results.
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PMID:Two sensitive and rapid chromogenic assays of fondaparinux sodium (Arixtra) in human plasma and other biological matrices. 1457

Recently we have shown that activation of inflammatory reaction and clotting can be found immediately after delivery in preterm lambs ventilated for respiratory distress syndrome (RDS). To investigate whether antenatal glucocorticoids would attenuate postnatal activation of the inflammatory reaction and clotting, we studied ventilated preterm lambs delivered by cesarean section, 24 h after antenatal administration of betamethasone or placebo. Blood was sampled before clamping the cord, 5, 10, and 15 min after delivery, and 2-hourly afterwards. Blood was used to determine oxygenation index, alveolar - arterial partial O(2) difference (AaDO(2)), AP50 titer (see text), polymorphonuclear leukocytes (PMNs), beta-glucuronidase, thrombin inhibition, activated partial thromboplastin time, and clot lysis time. Bronchoalveolar lavage fluid was sampled before clamping the cord and 30 min and 1, 2, 4, 6 and 8 h after delivery and was analyzed for elastase, thrombin, and protein. After removal of the lungs, static compliance and water content of the lungs were determined. We found that betamethasone-treated lambs had lower oxygenation index and AaDO(2) than controls. At birth, PMN levels were higher, and the beta-glucuronidase level was lower after betamethasone treatment. PMNs and beta-glucuronidase did not change in betamethasone-treated lambs, in contrast to controls. Thrombin inhibition, activated partial thromboplastin time, and clot lysis time did not change in betamethasone-treated lambs, in contrast to controls. In both groups, elastase and protein levels in bronchoalveolar lavage fluid increased; the thrombin level increased in controls. The static compliance was better, and the water content of the lung was lower in the betamethasone-treated lambs. We conclude that early systemic activation of inflammatory reaction and clotting in preterm lambs with RDS are attenuated by antenatal betamethasone administration. Whether this is a direct effect of betamethasone on the inflammatory reaction or a result of a reduced ventilatory support because of less severe RDS after antenatal betamethasone treatment remains to be elucidated.
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PMID:Antenatal glucocorticoids attenuate activation of the inflammatory reaction and clotting in preterm lambs. 1463 Nov 53

Monte Carlo/Extended Linear Response (MC/ELR) simulations have been conducted on 60 inhibitors of human factor Xa to determine the important interactions associated with their activity. A variety of physicochemical descriptors were configurationally averaged during the course of the simulations of each inhibitor bound to factor Xa and free in water. A regression equation was then derived; it reproduces the experimental inhibition data with a correlation coefficient, r(2), of 0.74, an rms error of 0.67 kcal/mol, and an average unsigned error of 0.60 kcal/mol using only two physically reasonable descriptors. The two factors that emerged as important in determining inhibitory potential are (1) favorable van der Waals interactions between protein and ligand and (2) direct hydrogen bonding between the inhibitor and protein. The conclusions were supported with structural analyses and results of MC/free energy perturbation (FEP) calculations.
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PMID:Analyses of activity for factor Xa inhibitors based on Monte Carlo simulations. 1466 22


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