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)

Blood coagulation studies were performed on 45 healthy, adult guinea pigs. Additionally thrombelastograms of 30 animals were recorded. Guineapigs revealed short partial thromboplastin times and euglobulin lysis times, but long prothrombin times and thrombin times. Fibrinogen values were within the range of human normal values. Biphasic ADP-induced aggregation of platelets, as occurs in man, was found in 29% of the animals. Short r (reaction time until the beginning of clot formation) and k times (time from the beginning of clot formation until an amplitude of 20 mm) of their thrombelastograms indicate, that whole blood clotting is enhanced in guineapigs. Higher maximum amplitudes in this species suggest a stronger clot stability than in man.
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PMID:Blood coagulation studies in guineapigs (Cavia porcellus). 317

Platelet fatty acids, platelet aggregations, and coagulation factors were measured in 27 rural blacks, 27 urban blacks and 39 urban whites. Platelets were significantly less aggregable to collagen and arachidonic acid in in both black groups as compared to whites (p less than 0.01), but there were no significant differences in ADP or epinephrine aggregation between these groups. Factor VIII coagulant activity was much higher in rural and urban blacks than whites (p less than 0.001), and the partial thromboplastin times were shorter (p less than 0.005). Platelet arachidonic acid showed a marked difference between the groups, being 16.4 +/- 5.4% of total platelet fatty acids in the rural blacks, 19.9 +/- 4.2% in the urban blacks and 22.6 +/- 3.3% in the whites (p less than 0.001). Whites had higher LDL and lower HDL cholesterol than blacks (p less than 0.005). These findings suggest that in addition to the well known association of raised LDL cholesterol and acute myocardial infarction, platelet aggregation patterns and platelet arachidonic acid levels may be associated risk factors in coronary thrombosis.
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PMID:Platelet aggregations, fatty acids, clotting factors and serum lipids in rural and urban blacks, and urban whites in South Africa. 317

Swiss albino mice were infected by the intraperitoneal route with P. berghei berghei malaria parasite, and platelets, white cell counts and some coagulation parameters were monitored in order to find out whether changes reported in man also occurred in the mice. Parasitaemia developed form the 2nd post-infection day and reached significant levels by the 4th-6th day. Reduced circulating platelets which reached severe thrombocytopenic levels were observed. parallel with the increasing degree of parasitaemia. Anaemia which progressed to severe degree was also observed as was a slight leucocytosis attributed to the presence of normal mouse erythrocytes in the peritoneal space. All untreated animals died by the 6th day of infection. Intramuscular chloroquine sulphate (20 micrograms/g body wt.) given for 7 days completely cured the malaria, and white cell and platelet counts were restored to preinfection levels in each animal about 2 weeks after treatment had ceased. Platelet hypersensitivity to exogenous ADP was observed within 48 hours of infection and persisted with the parasitaemia. Prothrombin time (PT) and activated partial thromboplastin time (APTT) were prolonged while clottable fibrinogen concentration was reduced.
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PMID:Platelet reactions in acute Plasmodium berghei infection in Swiss albino mice. 330 58

Protamine sulfate is considered a weak anticoagulant, yet little is known concerning the mechanism of this effect or its relation to prior heparin exposure. This investigation defined the influence of increasing doses of protamine, with and without prior heparin anticoagulation, on the activated clotting time (ACT), thrombin clotting time (TCT), prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen level, platelet count, and platelet aggregation to ADP in dogs (n = 8). Four doses of intravenous protamine sulfate (1.5, 3.0, 6.0, and 15.0 mg/kg) were studied in each animal, with at least 5 days between individual studies. Four dogs received heparin, 150 IU/kg 10 min prior to protamine sulfate administration, and four dogs received protamine sulfate alone. Protamine sulfate caused anticoagulation, both in the presence and absence of heparin, with significant changes occurring in the ACT, PTT, platelet count, and platelet aggregation. Relevant changes did not occur in the TCT, PT, or fibrinogen levels. Platelet effects were capable of causing bleeding with standard or excess use of protamine sulfate, especially if platelet numbers were already decreased, as might occur in surgical procedures where thrombocytopenia commonly accompanies major blood loss and replacement. The ACT, reflecting both the coagulation cascade and platelet function, was the test most profoundly affected by protamine overdosage, and therefore may be misleading as a measure of protamine reversal of heparin. The TCT, which is sensitive to heparin anticoagulation but not protamine-induced anticoagulation, should be more accurate in differentiating inadequate heparin reversal from the effects of excess protamine.
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PMID:Anticoagulant effects of protamine sulfate in a canine model. 339 95

The effects of diltiazem hydrochloride on exercise-induced changes in cardiovascular response, plasma renin activity, platelet function and blood coagulability were evaluated with multistage treadmill exercise in 20 patients who had systemic hypertension of stage 1 to 2 (World Health Organization classification). Heart rates, blood pressure, and pressure-rate product at rest, at peak exercise and in the recovery period were significantly reduced after 4 weeks of diltiazem administration, 180 mg/day. Plasma renin activity tended to increase after the medication. However, platelet adenosine diphosphate-induced aggregation sensitivity, prothrombin time, activated partial thromboplastin time, plasma fibrinogen concentration and antithrombin III activity did not change significantly. It is concluded that diltiazem could ameliorate the hyperresponsiveness of heart rate and BP to exercise in hypertensive patients without affecting blood coagulability.
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PMID:Effects of diltiazem hydrochloride on cardiovascular response, platelet aggregation and coagulating activity during exercise testing in systemic hypertension. 351 20

We have studied the biocompatibility properties of polymerizable phosphatidylcholine bilayer membranes, in the form of liposomes, with a view toward the eventual utilization of such polymerized lipid assemblies in drug carrier systems or as surface coatings for biomaterials. The SH-based polymerizable lipid 1,2-bis[1,2-(lipoyl)dodecanoyl]-sn-glycero-3-phosphocholine (dilipoyl lipid, DLL) and the methacryl-based lipid 1,2-bis[(methacryloyloxy)dodecanoyl]-sn-glycero-3-phosphocholine (dipolymerizable lipid, DPL) were studied in comparison to 'conventional' zwitterionic or charged phospholipids. We examined binding of serum proteins to liposomes and effects of liposomes on fibrin clot formation and on platelet aggregation. All types of liposomes tested bound complex mixtures of serum proteins with IgG being the most abundant bound component. DPL vesicles and anionic vesicles bound substantially more protein than other vesicle types. Polymerized DPL vesicles uniquely bound a protein of about 53 kDa which was not bound to other types of phosphatidylcholine liposomes. Likewise polymerized DPL vesicles, but not other types of phosphatidylcholine vesicles, caused a marked alteration in coagulation as measured by activated partial thromboplastin time (APTT) and prothrombin time (PT) tests; this effect was shown to be due to binding and depletion of clothing factor V by the DPL polymerized vesicles. Polymerized DPL liposomes and DLL liposomes in polymerized or nonpolymerized form, were without substantial effect on platelet aggregation. However, DPL nonpolymerized vesicles, while not causing aggregation, did impair ADP-induced aggregation of platelets. These studies suggest that SH based polymerizable lipids of the DLL type may be very suitable for in vivo use in the contexts of drug delivery systems or biomaterials development. Methacryloyl-based lipids of the DPL type seem to display interactions with the hemostatic process which militate against their in vivo utilization.
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PMID:Interactions of polymerizable phosphatidylcholine vesicles with blood components: relevance to biocompatibility. 359 6

A study was performed to evaluate decompression procedures suggested for use prior to Space Shuttle extravehicular activity. Hematological parameters were measured in 12 male human subjects before and after exposure in an altitude chamber to a 3-day staged decompression schedule, with simulated extravehicular activity. Following the exposure, significant increases occurred in white blood cell count and activated partial thromboplastin time, and platelet aggregate ratio was significantly decreased. Pre-exposure samples from subjects who were susceptible to formation of venous gas emboli (VGE) exhibited a significantly lower degree of ADP-induced platelet aggregation and a significantly higher amount of lymphocyte blastogenic transformation in response to the mitogen phytohemagglutinin than samples from VGE-resistant subjects. The results indicate that, following this decompression profile, small but significant changes occur in several hematological parameters, and that levels of certain parameters may be related to susceptibility to VGE formation during decompression.
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PMID:Hematological changes following repetitive decompressions during simulated extravehicular activity. 378 34

Formation of a hemostatic plug represents one of the earliest responses to vessel wall injury. Platelets react to any discontinuity in the vascular endothelium through initial contact, spreading, and formation of a thrombus (or aggregate). This development of a primary hemostatic plug requires platelet membrane receptors through which the adhesive macromolecules, von Willebrand factor (vWF) and fibrinogen, anchor platelets to the vessel wall and link them to each other. There are two receptor pathways--classic and alternative--for the binding of vWF to platelets; the latter induced by thrombin, and adenosine diphosphate (ADP) is shared with fibrinogen. Synthetic peptides, patterned after known binding domains of adhesive molecules, have been designed to inhibit their interactions with platelet receptors. A secondary hemostatic plug, composed of platelets enmeshed in fibrin, results from the action of thrombin, which is not only essential for formation of fibrin but also for exposure of platelet receptors for adhesive molecules and for "activation" of factors V and VIII. Thrombin generation is greatly enhanced through the activity of the prothrombinase complex formed on the surface of platelets, perturbed endothelial cells, and leukocytes. A pivotal event is activation of factor X through the intrinsic and extrinsic coagulation pathways. Binding of factors IXa and VIIa to the vascular endothelium represents a localized mechanism for factor Xa generation. Formation of a platelet and fibrin thrombus is controlled by regulatory mechanism: prostacyclin, endogenous heparin-antithrombin III complex, thrombomodulin-protein C-protein S system, and the fibrinolytic system. The balance of all components--vessel wall, platelets, adhesive and coagulation proteins, regulatory mechanisms--determines the effectiveness of the hemostatic plug in maintaining the structural and functional integrity of the circulatory system. An approach to detection of hemostatic derangements in patients at risk evolves from a full understanding of inherited and acquired deficiencies affecting each step of hemostatic plug formation and from selective use of laboratory tests.
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PMID:Formation and regulation of platelet and fibrin hemostatic plug. 380 19

In an earlier report on the kidney in systemic lupus erythematosus (SLE), we described a subset of patients with circulating anticoagulants; many had glomerular and arteriolar thrombosis in the absence of necrosis and subendothelial deposits. The present study extends these observations to a larger group of patients with SLE and a circulating anticoagulant, and compares its findings with those in patients with SLE without evidence of an anticoagulant. It demonstrates (1) a higher prevalence of clinically recognizable thrombotic events in the venous and arterial circulations in patients with SLE and a detectable anticoagulant; (2) a probable shortening in life span; (3) a higher prevalence of glomerular thrombi; (4) elevated levels of factor VIII antigen and von Willebrand factor; and (5) significantly lower platelet counts and decreased in vitro platelet aggregation in response to adenosine diphosphate, epinephrine, and collagen. Since prednisone treatment often results in improvement or disappearance of a prolonged partial thromboplastin time, the test most commonly used for screening of a circulating anticoagulant, we suggest that the prevalence of this abnormality may be underestimated in patients with SLE.
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PMID:Thrombosis in systemic lupus erythematosus. Relation to the presence of circulating anticoagulants. 392 65

(2R, 4R)4-methyl-1-[N alpha-(3-methyl-1,2,3,4-tetrahydro-8-quinoline- sulfonyl)-L-arginyl]-2-piperidine carboxylic acid monohydrate (MCI-9038) was found to be a potent synthetic inhibitor of thrombin. In concentrations as low as 1 microM, the thrombin time, prothrombin time, and partial thromboplastin time were more than doubled. The venom (Bothrops atrox) time was similarly prolonged. The drug also inhibited the thrombin-induced activation of factors VIII and XIII. While MCI-9038 in concentrations of 10(-4) M had no effect on platelet aggregation induced by collagen, ADP, epinephrine, and arachidonate, nanomolar concentrations inhibited thrombin-induced platelet aggregation and the release of platelet ADP. The drug also significantly inhibited the adhesion of thrombin-treated platelets to cultured bovine aortic endothelial cells. We conclude that MCI-9038 is an extremely potent inhibitor of the effects of thrombin on platelets and clotting factors.
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PMID:In vitro studies of a new synthetic thrombin inhibitor. 398 96


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