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)

One-stage prothrombin times of normal and of factor VII-deficient beagle plasma were determined with two types of beagle brain thromboplastin, one prepared from normal beagles and the other from factor VII-deficient beagles. There was little difference between the reagents in the prothrombin times obtained for normal plasma. However, when factor VII-deficient plasma was tested, reagent prepared from factor VII-deficient beagles gave considerably longer prothrombin times than were obtained with the normal reagent and the difference increased with increasing reagent concentration to a maximum at 140 mg/ml. Prothrombin times of a series of mixtures of normal and factor VII-deficient plasma indicated that the presence of only 1/90 part of normal plasma was necessary to compensate for the difference between the two reagents. Determination of the iron content of the reagent suggested that the microcirculation of an average brain contained some 1.8 g of whole blood. The finding that brain thromboplastin prepared from factor VII-deficient beagles is more sensitive to a deficiency of factor VII in plasma, presumably a result of the smaller quantity of factor VII present in the reagent, is compatible with the known kinetics of extrinsic coagulation.
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PMID:The influence of residual factor VII on the sensitivity of brain thromboplastin. 70 87

Rapid coagulation and fibrinolysis assays suitable for use with an imprecisely measured sample volume (either whole blood or plasma) have been developed, utilizing a technology based on paramagnetic iron oxide particles (PIOP) that move in response to an oscillating magnetic field. PIOP are combined with appropriate test reagents for clotting and thrombolysis assays and formulated as dry reagents within a capillary test chamber. The minima and maxima of the PIOP oscillations define a two-sided waveform that provides kinetic information on fibrin polymerization and lysis. Subject to the chemistry of the dry reagent formulation, the resulting waveform can be used to define clotting time, lysis onset time, or fibrinogen variables. Applications to one-stage prothrombin time and one-stage activated partial thromboplastin time tests have yielded assays with consistently good correlations with other test methods. Applications to fibrinolysis studies have yielded global assays of thrombolytic activity, in that the assay results reflect the interactions of multiple factors associated with the effectiveness of thrombolytic therapy. Depending on the components utilized in a particular reagent formulation, one can derive information about the activity of such factors as fibrinogen, plasminogen, and related inhibitors, as well as the lytic agent being administered. Use of these assays in a clinical setting should provide a rapid, convenient alternative to conventional testing of coagulation variables and a reliable method for monitoring thrombolytic therapy.
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PMID:Dry reagent technology for rapid, convenient measurements of blood coagulation and fibrinolysis. 201 64

The routine preoperative evaluation of pediatric patients often includes a history, physical examination, complete blood count, and urinalysis (UA). We retrospectively reviewed the records of 486 elective surgeries in children to determine the role of abnormal preoperative laboratory test results in perioperative management. Anemia or microcytosis was apparent in 17% of patients, and abnormal UA results were found in 15%. More than 80% of the abnormal UA results were historically known, clinically insignificant, or false-positives. Only five children had surgery canceled owing to abnormal laboratory tests: two owing to anemia, two to an abnormal UA, and one because of a prolonged partial thromboplastin time. Both children with anemia were treated with iron and subsequently underwent surgery without complication. Of the abnormal UAs, one was contaminated, and the cancellation of surgery resulted in a complication requiring emergency surgery. The other abnormal UA was a probable asymptomatic bacteriuria, and the infant later underwent surgery uneventfully. These data suggest that a routine UA adds little to the preoperative evaluation of a healthy child, and should be omitted.
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PMID:Preoperative laboratory testing of children undergoing elective surgery. 230 50

In a prospective study assessing haemostatic functions, the activated partial thromboplastin time was prolonged in 134 out of 10,229 patients studied, without an increase in the prothrombin or thrombin times; this abnormality persisted in only 37 of them on a new blood sample. A retrospective analysis was made of 265 patients who had such an isolated prolongation of the activated partial thromboplastin time on two successive blood samples: the causal abnormality remained unexplained in 135 patients; a well defined coagulation disorder without abnormal bleeding tendency was present in 110 patients (1 severe factor XII deficiency, 58 partial factor XI or XII deficiencies and 51 lupus anticoagulants); a bleeding disorder was diagnosed in 20 patients (8 haemophilias, 8 Von Willebrand's diseases, 4 factor VIII inhibitors). The well-iron efficacy of the activated partial thromboplastin time for detecting coagulation abnormalities is counter-balanced by some disadvantages such as the delay for biologic conclusions. In the preoperative assessment of haemostatic functions, rather than taking a routine approach, it would seem better to determine for each patient the need and the extent of biological testing according to the type of planned surgery, the clinical status of the patient and possible bleeding symptoms.
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PMID:[Successes and failures of the activated partial thromboplastin time in the preoperative evaluation]. 308 57

A bleeding disorder (von Willebrand's disease) was diagnosed in a 9-year-old male Himalayan cat examined because of persistent oral bleeding after routine dental extraction. Bleeding subsided after empirical treatment, which included prednisolone, vitamin K1, and transfusion of fresh blood, but recurred spontaneously after 8 months of apparent good health. Pertinent results of routine laboratory testing included an inconstant prolongation of the activated partial thromboplastin time and recurring iron-deficiency anemia. Assays of specific coagulation factors revealed low factor VIII coagulant activity and undetectable factor VIII-related antigen, a pattern considered to be diagnostic of von Willebrand's disease. This condition, not previously reported in a cat, should be included in the differential diagnosis when cats are examined because of abnormal bleeding.
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PMID:A bleeding disorder (von Willebrand's disease) in a Himalayan cat. 310 51

Coagulopathy is a hallmark of severe ferrous sulfate poisoning in humans and laboratory animals. Although nontransferrin-bound Fe3+ is thought to initiate the disorder, little is known about how it interferes with blood coagulation. At iron concentrations comparable to those of previous animal investigations, we reproduced the coagulopathy, in other words, the dose-related prolongation of the prothrombin, thrombin, and partial thromboplastin time, in human plasma in vitro. Studies of the mechanism by which iron prevents a normal plasma coagulation revealed that the proenzymes of the coagulation cascade and fibrinogen were not damaged by iron. Fibrinogen coagulability and fibrin monomer aggregation were unaffected by very high iron concentrations. Instead, thrombin was markedly inhibited by iron in its clotting effect on fibrinogen and, specifically, in its fibrinopeptide A-generating capacity, the inhibitory effect being reversible upon iron removal by EDTA chelation and gel filtration. Thrombin generation in the presence of iron was reduced as well, indicating an inhibition of one or several other enzymes of the intrinsic coagulation cascade. Because the amidolytic activity of human thrombin as well as factor Xa, kallikrein, and bovine trypsin was also reversibly suppressed by ferrous sulfate as well as ferric citrate, we consider it likely that the coagulopathy occurring in iron poisoning is the consequence of a general, physiologically important phenomenon: the susceptibility of serine proteases to nontransferrin-bound Fe3+.
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PMID:Blood coagulation and acute iron toxicity. Reversible iron-induced inactivation of serine proteases in vitro. 642 70

Calves inoculated with Sarcocystis cruzi sporocysts developed severe anemia 4 weeks later. The anemic crisis was paralleled by a hyperbilirubinemia, with up to 88% of the increased total bilirubin attributed to indirect reacting bilirubin. The anemia was characterized as normocytic and normochromic. In a few instances, according to Coombs's tests (antiglobulin test) and erythrocyte eluates from infected calves, immunoglobulin G was associated with the RBC membrane. In the histopathologic examinations of tissues from calves dying during the anemic crisis, there was deposition of iron in the splenic red pulp. The hematologic studies supported the claim that the anemia in acute bovine sarcocystosis is an extravascular hemolytic event, probably with an immunologic basis. In the coagulation studies, consumption coagulopathy consistent with disseminated intravascular coagulation was seen to occur during acute sarcocystosis. At 4 weeks after inoculations were done, there were prolongations of activated partial thromboplastin and 1-stage prothrombin times and decreased functional fibrinogen concentration, and thrombocytopenia, although increase of fibrinogen-fibrin degradation products were not demonstrable. These findings indicate that endothelial parasitism by schizonts of S cruzi may cause endothelial damage, resulting in coagulation abnormalities that include disseminated intravascular coagulation.
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PMID:Hematologic and coagulation abnormalities in acute bovine sarcocystosis. 642 7

Lactoferrin is a prominent component of neutrophil secondary granules, and its blood concentration is increased in certain inflammatory diseases. In contrast to the well-described biochemical characterization of lactoferrin as an iron-binding protein, its physiologic role in the regulation of inflammation and other host defense mechanisms is unclear. In this report, we provide evidence that lactoferrin has a potent heparin-neutralizing activity during thrombin inhibition by the serine proteinase inhibitors (serpins) antithrombin and heparin co-factor II. Activated neutrophil supernatant, which contains lactoferrin and other heparin-binding proteins, could neutralize the heparin-dependent antithrombin-thrombin inhibition reaction. The addition of lactoferrin to plasma corrected the heparin-induced prolongation of blood plasma coagulation as measured by the activated partial thromboplastin time (aPTT). Treatment of whole blood with specific inflammatory mediators, fMLP, lipopolysaccharide (LPS), and tumor necrosis factor-alpha (TNF-alpha) increased the concentration of both plasma lactoferrin and platelet factor 4 while inhibiting the blood anticoagulant activity of heparin as measured by the aPTT. These results suggest that the prothrombotic sequelae of some inflammatory processes may be partly due to various agonists that release neutrophil lactoferrin, which can then neutralize glycosaminoglycan-dependent serpin-thrombin inhibition reactions.
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PMID:Neutralization of heparin activity by neutrophil lactoferrin. 781 95

The aim of this prospective study was to obtain the first human safety and magnetic resonance (MR) imaging results with a new formulation of superparamagnetic iron oxide (SPIO) (SHU 555 A). The SPIO was tested at four iron doses, from 5 to 40 mumol/kg. Laboratory tests and clinical measurements were done in 32 healthy volunteers for up to 3 weeks after administration. MR imaging at 1.5 T was performed before and 8 hours to 14 days after fast intravenous injection (500 mumol Fe/min) of the SPIO (six subjects per dose). Results of this phase I study demonstrate that SHU 555 A at a concentration of 0.5 mol Fe/L was well tolerated. A dose-dependent minor increase in activated partial thromboplastin time, which remained within the normal range, was seen. All doses of SPIO caused a signal loss in both liver and spleen (P < .05) with a spin-echo sequence (TR = 2,300 msec, TE = 45 msec). The signal losses in the liver 8 hours after contrast agent injection were 58%, 79%, 82%, and 87% for the 5, 10, 20, and 40 mumol Fe/kg doses, respectively. The corresponding signal losses in the spleen were 23%, 45%, 65%, and 78%, respectively. The doses that reduced signal intensity by half were 3.1 mumol Fe/kg for the liver and 12.8 mumol Fe/kg for the spleen. The results suggest that the new SPIO formulation is a safe and efficient MR contrast agent.
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PMID:Contrast-enhanced MR imaging of liver and spleen: first experience in humans with a new superparamagnetic iron oxide. 798 10

Vertebrate ferredoxins are 12-14-kDa iron-sulfur proteins, some of which transfer electrons to mitochondrial cytochrome P450s. The function of many of these cytochrome P450s is to catalyze stereospecific hydroxylation of endogenous steroids. As part of our interest in the kidney mitochondrial 1 alpha-hydroxylation of 25-hydroxyvitamin D3, we have constructed an expression plasmid coding for a fusion protein containing the chick kidney ferredoxin. We subcloned chick kidney ferredoxin cDNA, obtained from our vitamin D-deficient chick kidney library by polymerase chain reaction (Brandt, M. E., Gabrik, A. H., and Vickery, L. E. (1991) Gene (Amst.) 97, 113-117) into Qiagen's pQE9, which contains an N-terminal 6xHis tag (peptide sequence for 6 adjacent histidines present in the recombinant proteins). The coding sequence was preceded by a factor Xa cleavage site. The resulting plasmid, pQTcFdx, was overexpressed in Escherichia coli, and the soluble fusion protein was purified from the cell lysate in one step by Ni(II)-nitrilotriacetic acid-agarose chromatography. We obtained 7-10 mg of greater than 99% homogeneous fusion protein from a 1-liter culture and 4-6 mg of mature ferredoxin cleaved by factor Xa. The fusion protein possessed an absorption spectrum and an electron paramagnetic resonance spectrum quantitatively indistinguishable from those published for ferredoxin purified from adrenal glands and placenta or expressed in E. coli with another vector. The fusion protein was active in supporting the 1 alpha-hydroxylation of 25-hydroxyvitamin D3 in a reconstitution assay of a solubilized, partially purified preparation of cytochrome P450 from vitamin D-deficient chick kidney. We conclude that the procedure described here is an efficient way to produce and purify vertebrate ferredoxin; the [2Fe-2S] cofactor is assembled in vivo and effectively incorporated into the fusion protein in E. coli; slight alterations at the N terminus do not alter incorporation of the [2Fe-2S] cofactor or the biological activity of ferredoxin, and post-translational modifications, such as phosphorylation, are not an absolute requirement for ferredoxin electron transporting activity. The recombinant ferredoxin can be used for physical studies and other structure-function studies.
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PMID:Overexpression in Escherichia coli and affinity purification of chick kidney ferredoxin. 849 94


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