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:3.4.21.5 (thrombin)
33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A method to increase the amount and improve the bioactivity of heparin (HEP) immobilized on a polymer surface was developed. The surface of polyurethane-urea (PU) coated glass beads was first modified with diisocyanates, followed by surface grafting of polyfunctional polymers (PFP), including: poly(vinyl alcohol), poly(ethyleneimine), and poly(allylamine). The functional groups of the surface grafted PFP (-OH, -NH, or -NH2) were modified with diisocyanates (TDI) to amplify the surface concentration of isocyanate groups, alpha, omega-diamino-terminated polyethylene oxide (PEO; molecular weight, 4,000 daltons) was then coupled to the surface grafted PFP, and the free amino groups were derivatized with TDI. Finally, HEP was coupled to the amplified surface through free -NCO groups of PU-PFP-PEO. The surfaces were quantified during each step of the procedures for -NCO groups and HEP. All grafted surfaces showed a four to eightfold increase in -NCO content and a twofold increase in immobilized HEP content compared with HEP immobilized directly onto the PU surface. The HEP bioactivity tests (including activated partial thromboplastin time, thrombin times, and factor Xa) demonstrated an increased bioactivity of HEP when immobilized through PFP-PEO compared with PFP and PU alone.
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PMID:Heparin immobilization by surface amplification. 145 39

Three novel methods, recently developed by us, for the synthesis of non-thrombogenetic materials were reviewed. The first was the utilization of poly(vinyl sulfonate) as a heparinoid and a newly synthesized polymerizable-thrombin-inhibitor. The chemicals were grafted onto the surfaces of materials. The second was the use of thrombin-substrate-analog peptide. The immobilized peptide was decomposed by blood coagulation factors and inhibited thrombus formation on the surface. The third method was the enhancement of endothelialization by immobilization of bio-signal molecules. The immobilized biosignals remarkably accelerated the growth of endothelial cells.
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PMID:Non-thrombogenicity by novel surface modification methods. 158 84

A new class of biomaterials, called "bioartificial polymeric materials", was prepared blending a segmented polyurethane (PU) with fibrinogen (FBNG); and poly(acrylic acid) (PAA), poly(acrylamide) (PAAM), poly(vinyl alcohol) (PVAL), with collagen (CLG), respectively. The PU-FBNG material was processed through a spraying, phase-inversion technique to fabricate porous tubular conduits. FBNG was subsequently converted into covalently cross-linked fibrin (FBN) through the action of thrombin (Th), fibrin-stabilizing factor (FSF), and calcium ions. Differential scanning calorimetry (DSC) showed the cross-linked blend was more stable than native cross-linked FBN. Tensile behaviors of the PU-FBN materials closely matched those of a natural artery on varying the ratio PU/FBN. Implantation experiments in the rat model showed a mature internal capsule and good tissue organization of PU-FBN (50%) grafts in the regenerated arterial wall. However, 50% of FBN did not assure adequate mechanical resistance, and aneurysmal changes were seen in some grafts. DSC of CLG-based materials, processed by casting, showed that the synthetic component offered definite advantage compared to the CLG denaturation temperature, particularly noticeable for CLG-PAA and CLG-PVAL blends. Material advantages and drawbacks are discussed.
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PMID:Bioartificial polymeric materials obtained from blends of synthetic polymers with fibrin and collagen. 186 55

This report describes a method of bleeding control at dental extraction sites using medicaments (thrombin, cocaine, Amicar, Surgicel) in conjunction with a dental appliance containing vinyl polysiloxane silicone putty (Optosil) to provide greater coverage and pressure at the extraction sites. The acrylic splint was used to control bleeding in a 15-year-old male, with an aplastic pancytopenia anemia, who had required removal of severely mobile exfoliating teeth prior to a bone marrow transplantation procedure.
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PMID:Bleeding control after extractions in a patient with aplastic anemia during bone marrow transplantation: report of case. 264 46

Commercially obtained (Diosynth) heparin was covalently bonded to poly (vinyl alcohol) (PVA) hydrogels and to polyethylene oxide (PEO) hydrogels activated by tresyl chloride. We found that as tresyl chloride activation of PVA increased, the specific activity of the bound heparin toward thrombin and antithrombin decreased by nearly a factor of 10 and that commercial heparin bound to PEO had nearly ten-fold greater activity than when bound to PVA at comparable concentrations. These findings suggest that the long 'leash' provided by PEO hydrogels may give the heparin more access to the thrombin-antithrombin pair than the tight bond to PVA, and that crowding of heparin units on a surface limits access of the thrombin-antithrombin pair.
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PMID:Activity toward thrombin-antithrombin of heparin immobilized on two hydrogels. 271 28

Copolymers of poly/vinyl alcohol-acrylic acid/ with various content of sulphate and carboxyl groups have been synthetized and tested for their in vitro effect on blood coagulation. The results indicate that the sulphated copolymers display an inhibitory effect but there is a requirement in the charged groups of about 20% in the molecule to possess effective anticoagulation. The biochemical mechanism of their actions is complex, i.e. the inhibition of blood clotting is a consequence of both the accelerated inactivation rate of thrombin by antithrombin-III and a direct inhibitory effect on the thrombin-fibrinogen reaction. Moreover, additional effects may occur on other blood coagulation enzymes than thrombin, depending on the chemical composition of the copolymers.
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PMID:Anticoagulant effect of sulphated poly/vinyl alcohol-acrylic acid/copolymers. 295 93

We studied the effect of the methanol extract of garlic bulbs (EOG) and of three pure components isolated from it (F1, F2, F3), on human platelet aggregation induced by ADP, epinephrine, collagen, thrombin, arachidonate, PAF, and the ionophore A-23187. Incubation of PRP with EOG, either in methanol or in homologous PPP, inhibits platelet aggregation induced by all of the above mentioned agonists. F1, F2, and F3 also inhibit platelet aggregation, however, F3 was about four times more potent. Addition of EOG or F3 to platelets that have already been irreversibly aggregated by 10 microM ADP, induces rapid deaggregation. Inhibition of aggregation was still present after three hours. The inhibitory effect persisted even after the treated platelets were Gel-Filtered (GFP) or separated from plasma through a metrizamide gradient and resuspended in new homologous PPP. Thrombin-induced release of ATP from GFP was inhibited by 75-80% after EOG or F3 treatment. Incorporation of [3-H]-arachidonate by intact platelets was decreased by 50-60% in treated platelets. However, platelets incubated with the inhibitors after incorporation of radiolabeled arachidonate, although did not aggregate, produced, after thrombin activation similar amounts of radiolabeled TXB2 and lipoxygenase products as the controls. Electron microscopy of inhibited platelets, in the presence of thrombin, showed no degranulation but an increase of spherical forms. Our results suggest that the effects described might be mediate by a perturbation of the physicochemical properties of the plasma membrane rather than by affecting arachidonate or calcium metabolism in the cells. Chemical structures of F1, F2 and F3 have been provisionally assigned: F1 is diallytrisulfide, F2 is 2-vinyl-1,3-dithiene, and F3 is most probably allyl 1,5-hexadienyltrisulfide.
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PMID:Effects of garlic extract and of three pure components isolated from it on human platelet aggregation, arachidonate metabolism, release reaction and platelet ultrastructure. 641 74

Cyclic guanosine 5'-monophosphate (cGMP) phosphodiesterase (PDE) regulates the level of cGMP on transduction of a visual signal in vertebrate photoreceptor cells. Two identical inhibitory PDE gamma subunits (Pgammas) block catalytic activity of PDE-alpha and -beta subunits (Palphabeta) in the dark. The primary regions of Pgamma involved in the interaction with Palphabeta are a central polycationic region, Pgamma-24-45, and a C-terminal region of Pgamma. Recently, we have shown that the C-terminal region of Pgamma, which is the major Pgamma inhibitory domain, blocks PDE activity by binding to the catalytic site of PDE (Artemyev, N. O., Natochin, M., Busman, M., Schey, K. L., and Hamm, H. E. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 5407-5412). Here, we localize the site on the rod cGMP PDE alpha subunit that binds to the central polycationic domain of Pgamma. This site is located within a region that links a second noncatalytic cGMP binding site with the catalytic domain of PDE. A polypeptide coresponding to this region, Palpha-461-553, expressed as a glutathione S-transferase fusion protein in Escherichia coli and isolated after cleavage of the fusion protein with thrombin, blocks inhibition of PDE activity by Pgamma. In addition, Palpha-461-553 binds to the Pgamma-24-45 region (Kd, 7 microM), as measured by a fluorescent increase in a Pgamma-24-45Cys peptide labeled with 3-(bromoacetyl)-7-diethylaminocoumarin. The Palpha-461-553 region was further characterized by using a set of synthetic peptides. A peptide corresponding to residues 517-541 of Palpha (Palpha-517-541) effectively suppressed inhibition of PDE activity by Pgamma and bound to Pgamma-24-45Cys labeled with 3-(bromoacetyl)-7-diethylaminocoumarin (Kd, 22 microM). Palpha-517-541 also competes with the activated rod G-protein alpha-subunit for binding to Pgamma labeled with lucifer yellow vinyl sulfone. This suggests that light activation of rod PDE by the G-protein transducin involves competition between transducin alpha-guanosine 5'-triphosphate and Palpha-517-541 for binding to the Pgamma-24-45 region. Based on the results, we propose a linear model of interactions between catalytic and inhibitory PDE subunits.
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PMID:An interface of interaction between photoreceptor cGMP phosphodiesterase catalytic subunits and inhibitory gamma subunits. 870 12

We determined plasma levels of thrombomodulin, thrombin-antithrombin III complex (TAT), protein C, protein S, and plasmin-alpha 2 plasmin inhibitor complex (PIC) before and after hemodialysis in 54 patients receiving chronic hemodialysis, to evaluate the blood-coagulation system and to evaluate the antithrombogenicity of various dialyzer membranes. Predialysis levels of thrombomodulin and TAT were both significantly increased compared with normal control values, but levels of protein C, protein S, and PIC were not changed. In patients dialyzed with ethylene vinyl alcohol (EVAL) and polysulfone membranes, postdialysis levels of thrombomodulin, TAT, protein C, protein S, and PIC were not significantly different from the predialysis levels. However, in patients dialyzed with regenerated cellulose and polymethyl-methacrylate (PMMA) membranes, postdialysis levels of thrombomodulin, TAT, and PIC were significantly higher than predialysis levels. We conclude that patients on maintenance hemodialysis were considered to be in a state of hypercoagulability before hemodialysis, and a single hemodialysis session using regenerated cellulose and PMMA membrane may have caused injury to vascular endothelial cells, hypercoagulability, and enhancement of fibrinolytic activity.
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PMID:Evaluation of blood coagulation-fibrinolysis system in patients receiving chronic hemodialysis. 943 76

A new one-step procedure for entrapping proteases into a polymeric composite calcium alginate-poly(N-vinyl caprolactam) hydrogel was developed that provided 75-90% retention of the activity of entrapped enzymes compared to soluble ones. Properties of entrapped carboxypeptidase B, trypsin, and thrombin were investigated. The immobilized enzymes were active within a wide pH range. The temperature optima of entrapped trypsin and carboxypeptidase B were approx 25 degrees C higher than that of the soluble enzymes, and the resistance to heating was also increased. The effects of various polar and nonpolar organic solvents on the entrapped proteases were investigated. The immobilized enzymes retained their activity within a wide concentration range (up to 90%) of organic solvents. Gel-entrapped trypsin and carboxypeptidase (CPB) were successfully used for obtaining human insulin from recombinant proinsulin. The developed stabilization method can be used to catalyze various reactions proceeding within wide pH and temperature ranges.
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PMID:Stabilization of proteases by entrapment in a new composite hydrogel. 910 Mar 46


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