Partial thromboplastin time test with kaolin: diagnosis of haemophilia and Christmas disease without natural reference plasmas

Leptospira Infection Interferes with the Prothrombinase Complex Assembly during Experimental Leptospirosis

Leptospirosis is a worldwide zoonotic and neglected infectious disease of human and veterinary concern, caused by pathogenic Leptospira species. Although bleeding is a common symptom of severe leptospirosis, the cause of hemorrhage is not completely understood. In severe infections, modulation of hemostasis by pathogens is an important virulence mechanism, and hemostatic impairments such as coagulation/fibrinolysis dysfunction are frequently observed. Here, we analyze the coagulation status of experimentally infected hamsters in an attempt to determine coagulation interferences and the origin of leptospirosis hemorrhagic symptomatology. Hamsters were experimentally infected with L. interrogans. The lungs, kidneys, and livers were collected for culture, histopathology, and coagulation assays. L. interrogans infection disturbs normal coagulation in the organs of animals. Our results suggest the presence of a thrombin-like factor or FX activator, which is able to activate FII in the leptospirosis organ extracts. The activity of those factors is accelerated in the prothrombinase complex. Additionally, we show for the first time that live leptospires act as a surface for the prothrombinase complex assembly. Our results contribute to the understanding of leptospirosis pathophysiological mechanisms and may open new routes for the discovery of novel treatments in the severe manifestations of the disease.

A proteinase inhibitor from Caesalpinia echinata (pau-brasil) seeds for plasma kallikrein, plasmin and factor XIIa

Caesalpinia echinata is a tree belonging to the Leguminosae family. The red color of the trunk, looking like burning wood (‘brasa’ in Portuguese), is the origin of the name Brazil. Seeds of leguminous plants contain high amounts of serine proteinase inhibitors that can affect different biological processes. Here we show that a protein isolated from seeds of C. echinata is able to inhibit enzymes that participate in blood coagulation and fibrinolysis. This inhibitor (CeKI) was purified to homogeneity by ion exchange and reversed-phase chromatography. SDS-PAGE indicated a single polypeptide chain with a molecular mass of 20 kDa. CeKI inhibits human plasma kallikrein (K i=3.1 nM), plasmin (K i=0.18 nM), factor XIIa (K i=0.18 nM), trypsin (K i=21.5 nM) and factor Xa (K i=0.49 mM). CeKI inhibited kinin release from highmolecular- mass kininogen by kallikrein in vitro. The N-terminal sequence, determined by automatic Edman degradation, identified the inhibitor as a member of the Kunitz family. The secondary structure, determined by circular dichroism, is mainly a random coil followed by β-sheet structure. The action of CeKI on enzymes of the blood-clotting intrinsic pathway was confirmed by prolongation of the activated partial thromboplastin time.

Leucaena leucocephala serine proteinase inhibitor: primary structure and action on blood coagulation, kinin release and rat paw edema

A serine proteinase inhibitor isolated from Leucaena leucocephala seeds (LlTI) was purified to homogeneity by acetone fractionation, ion exchange chromatography, gel filtration and reverse phase chromatography (HPLC). SDS-PAGE indicated a protein with M(r) 20000 and two polypeptide chains (alpha-chain, M(r) 15000, and beta-chain, M(r) 5000), the sequence being determined by automatic Edman degradation and by mass spectroscopy. LlTI is a 174 amino acid residue protein which shows high homology to plant Kunitz inhibitors, especially those double chain proteins purified from the Mimosoideae subfamily. LlTI inhibits plasmin (K(i) 3.2 x 10(-10) M), human plasma kallikrein (K(i) 6.3 x 10(-9) M), trypsin (K(i) 2.5 x 10(-8) M) and chymotrypsin (K(i) 1.4 x 10(-8) M). Factor XIIa activity is inhibited but K(i) was not determined, and factor Xa, tissue kallikrein and thrombin are not inhibited by LlTI. The action of LlTI on enzymes that participate in the blood clotting extrinsic pathway is confirmed by the prolongation of activated partial thromboplastin time, used as clotting time assay. The inhibition of the fibrinolytic activity of plasmin was confirmed on the hydrolysis of fibrin plates. LlTI inhibits kinin release from high molecular weight kininogen by human plasma kallikrein in vitro and, administered intravenously, causes a decrease in paw edema induced by carrageenin or heat in male Wistar rats. In addition, lower concentrations of bradykinin were found in limb perfusion fluids of LlTI-treated rats.

An artificial 'haemophilic' plasma for one-stage factor-VIII assay

An 'artificial' plasma for one-stage factor-VIII assays is made by incubating human plasma with EDTA, to destroy factor VIII, and afterwards removing the anticoagulant by dialysis. Bovine factor V is then added to a given level. In the assay, contact activation is controlled by adding contact product. It was confirmed that factor-VIII activity was destroyed and that the EDTA was freely dialysable. The fibrinogen in the treated plasma clotted normally with thrombin. Likely variation in the factor-V activity was found not to be critical. The concentration of fibrinogen and other factors was adequate. Variation between batches was small. The artificial plasma yielded assay results closely comparable to haemophilic plasma in samples with factor-VIII activities in the range 0.01--20.0 iu/ml; the mean results in the artificial system were estimated to be 0.997 x those in haemophilic plasma, with a 95% confidence interval of 0.901--1.103. Biological variability in individual assays was smaller in the artificial system than when haemophilic plasma was used. Instability at the bench was more often detected in the artificial system than in haemophilic plasma assays, but the effect was eliminated from the results by obtaining duplicated readings in a balanced order.

An approach to the evaluation of hemostasis

Effective hemostasis may be adequately and quickly evaluated using tests that are readily available in the usual hospital laboratory. This evaluation includes peripheral smear for platelet morphology and number, platelet count, bleeding time, activated partial thromboplastin time (aPTT), prothrombin time (PT), and clot retraction. Normal results of these tests exclude all but the mildest disturbances of hemostasis.

Simple screening tests for the diagnosis of isolated clotting factor defects. With special reference to 'contact factor' defects

Reagents may be prepared from normal plasma and used with the prothrombin time and partial thromboplastin time tests to distinguish isolated defects of factors I, II, VII, VIII, IX, X, XI, or XII.

Coagulation changes during the steady state in homozygous sickle-cell disease in Jamaica

Coagulation studies were carried out in 117 Jamaicans with homozygous sickle-cell disease in the steady state, and 40 local controls. The patients had significantly higher factor-VIII levels, higher platelet counts, lower factor-V and plasminogen levels, shorter thrombin times and higher serum fibrinogen degradation products (FDP) than the control group. The low factor-V and plasminogen levels, and high FDP levels, might be explained by activation of the coagulation system and continuous clot lysis even in the absence of painful crisis. The high factor-VIII levels and short thrombin times found in these patients could not be explained.

Diagnosis of haemophilia: use of an artificial factor-VIII-deficient human plasma system

An artificial clotting system deficient in factor VIII has been made from normal human plasma. Factors XII and XI are supplied as ;activation product'. An eluate from Al(OH)(3), which has been incubated with normal plasma, supplies factors X and IX in their ;plasma' (unactivated) form with II. Factor V is provided as the supernatant after the Al(OH)(3)- treated plasma has been precipitated at one-third saturation with (NH(4))(2)SO(4). Fibrinogen is freed of factor VIII by freezing and thawing a lyophylized preparation and then added. Of these, activation product and the fibrinogen may be prepared in advance and stored frozen, and the eluate and supernatant may be made on the day of testing. A phospholipid source and CaCl(2)-solution are also required. In use, a patient's and a control plasma are first diluted in a mixture of the eluate, supernatant, and fibrinogen solution, and clotting times are recorded after completing the system by adding the phospholipid, activation product, and calcium chloride. The clotting times from the mixtures containing the patient's and the control plasmas may then be compared.