摘要:

A recently-introduced automated method for the determination of plasma fibrinogen is based on the principle of von Clauss, combined with photometric detection: after addition of thrombin, the coagulation time is determined by measuring the change in absorption at 405 nm. This method was evaluated and compared with the original coagulometric Clauss assay and with the prothrombin time (PT)-derived automated method. The inter-assay coefficient of variation of the Clauss-derived assay was lower (14.1, 3.8 and 4.6%) than the PT-derived assay (16.1, 7.5 and 10.5%, respectively) at all three fibrinogen levels tested (1.2, 4.0 and 7.5 g/1). The correlation between the assays was investigated according to the method of Passing and Bablok and could be described as follows: Clauss-derived=0.79 (PT-derived) + 0.66; Clauss-derived=1.12 (Clauss) + 0.143. The interference of heparin (< 1.5 U/ml), haemoglobin (< 30 μmol/l), bilirubin (< 200 μmol/l) and triglycerides (< 5.5 mmol/1) in the Clauss-derived assay was negligible. The effects of fibrinogen degradation products on the Clauss-derived assay were comparable with the effects on the Clauss assay, in contrast to the effects on the PT-derived assay. In conclusion, the Clauss-derived assay is a specific and precise automated method to determine fibrinogen concentrations in plasma, which is not liable to interference from different pathophysiological substances.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

We have standardized a simple screening test for abnormalities of the protein C anticoagulant system. The test is basically a modified prothrombin time in which one aliquot of a test plasma is incubated for 3 min at 37°C with Protac® and another is incubated with buffer. During the incubation the Protac® activates both protein C and factor V. The plasmas are then clotted with thromboplastin plus Ca2+, and the clotting time difference reflects the ability of the activated protein C (APC) to inactivate factor Va. With the use of Thromboplastin C Plus as the activator, clotting time differences found in 31 normal subjects (10.4 ± 3.5 s, mean ± 2SD) were distinct from clotting time differences found in 57 of 58 subjects with established APC-resistant factor Va (3.6 ± 3.0 s). In addition, the Protac® -based test detected six of seven patients with isolated protein C deficiency and 20 of 28 patients with isolated protein S deficiency. Because of the reported high prevalence of heterozygous APC-resistant factor Va in Caucasian populations, it should be particularly useful in determining whether this genetic risk is present in individuals who have experienced or are at increased environmental risk of venous thrombosis.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Hypoprothrombinemia is an uncommon hereditary coagulation defect characterized by low levels of biologically active prothrombin. Automated fluorescence-based DNA sequence analysis of amplified genomic DNA was used to define prothrombin gene regions from a patient with severe functional hypoprothrombinemia and little detectable prothrombin antigen. Two changes that alter amino acid sequence were observed: a deletion of one nucleotide (-G, 7248/7249) in exon 8 of one allele, causing a frameshift at codon 249/250 that results in premature termination of translation; and a C&U279E;T change resulting in the substitution of tryptophan (TGG) for arginine (CGG) at amino acid 340 in exon 10 of the prothrombin gene. Computer modeling of the thrombin molecule confirmed that arginine 340 is located at the surface of the thrombin molecule, which points to the aqueous solvent. As tryptophan is a highly hydrophobic amino acid, the Arg&U279E;Trp change may be associated with instability of the thrombin molecule.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

The serum levels of thrombopoietin (TPO) were measured in 16 patients with thrombotic thrombocytopenic purpura (TTP), 12 with hemolytic uremic syndrome (HUS), 10 with aplastic anemia (AA), 10 with disseminated intravascular coagulation (DIC), and 71 with idiopathic thrombocytopenic purpura (ITP). The serum TPO levels were measured with a sensitive sandwich enzyme-linked immunosorbent assay. The serum TPO level in the ITP group (1.68 ± 0.85 fmol/ml) were not significantly increased compared with those of the normal subjects. The TPO levels in the TTP (2.77 ± 1.38 fmol/ml) and HUS groups (5.77 ± 4.41 fmol/ml) were higher than those of the normal subjects. The patients with AA (12.7 ± 8.0 fmol/ml) and those with DIC (13.3 ± 5.7 mol/ml) had significantly higher serum TPO levels than did the normal subjects and ITP patients. The TPO levels were well correlated with the platelet counts in the TTP patients, and were negatively correlated with the platelet counts in the ITP patients. These results suggest that the serum TPO levels in some thrombocytopenic diseases are regulated not only by the platelet count and the megakaryocyte mass, but also by other factors.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

The dynamic process of fibrinolysis induced by tissue plasminogen activator was examined using a rheological technique. Change in a rheological parameter (logarithmic damping factor) of whole blood and platelet-free plasma during fibrinolysis was largely dependent on the initial concentration of tissue plasminogen activator. Addition of activated partial prothrombin time reagent allowed determination of the time both of onset and end of fibrinolysis without affecting the coagulation process. The changes in the clot structure of fibrin during fibrinolysis were observed with a scanning electron microscope and compared with the timedependent behavior of the logarithmic damping factor. Differences in the logarithmic damping factor during fibrinolysis were evident in alteration of the network structure of clots. It will be shown that the present rheological technique is useful for examining the concentration dependence of fibrinolytic reagent on fibrinolysis as well as for monitoring the dynamic process of fibrinolysis.

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID

ISSN:0957-5235    

出版商:OVID    

年代:1997

数据来源: OVID