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At least 991 records · Page 55Linked to original sources
PubMed2004

Specific detection of human coagulation factor IX in cynomolgus macaques.

After screening for species-specific antihuman factor (F)IX monoclonal antibodies, we found that antibody 3A6 did not bind to cynomolgus FIX. The 3A6 epitope was found to include Ala262 of human FIX. The 3A6 antibody was used as a catching antibody in an enzyme immunoassay (EIA) for specific detection of human FIX in cynomolgus macaque plasma. No significant increase of substrate hydrolysis was observed when EIA buffer containing cynomolgus macaque plasma was subjected to the 3A6-based EIA. Addition of up to 30% cynomolgus macaque plasma or canine plasma to the assay did not alter detection of human FIX. Three cynomolgus macaques were injected with human FIX (10 U kg-1; i.v.) and the circulating human FIX was quantified in the macaque plasma. The FIX level in the circulation increased to 470 +/- 37.6 ng mL-1 at 1 h after the injection and gradually decreased to 1.79 +/- 1.1 ng mL-1 by day 5, which is approximately 0.06% of the normal human plasma FIX concentration. These data suggest that the cynomolgus macaque can be used as a primate model for studying hemophilia B gene therapy by transduction of macaque organs with vectors to express human FIX in vivo and detection of human FIX using the 3A6 monoclonal antibody.

Animals↗
PubMed1990

[Paradoxical bleeding as a complication of the treatment of hemophilia with factor VIII and factor IX preparations].

Paradoxical bleedings are complications occurring under replacement therapy in haemophiliacs by disturbancies of the primary haemostasis. They have been observed during treatment with factor-VIII- and prothrombin-complex concentrates of long duration and in high dosage. Clinical complications, for example delayed wound healing as well as spontaneous bleedings into the skin and from the mucous membranes, have been observed in one quarter of haemophiliacs under substitution therapy. In one third of these patients pathological parameters of primary haemostasis (prolonged bleeding time, reduced retention, retraction, ADP- and collagen-induced aggregation and the platelet factor 3 release) were found out. The following mechanisms or substances may be the cause for these disturbancies: 1. fibrinogen and factor-VIII split products 2. high content of proteins predominantly fibrinogen and factor-VIII-related antigen 3. antigen-antibody reactions 4. development of inhibitors against the Willebrand factor. For treatment of the paradoxical bleedings freshly prepared cryoprecipitate, prednison and Etamsylatum have been used.

Anticoagulants↗
PubMed1999

Assessment of potential thrombogenicity of coagulation factor IX concentrates in an in vitro model of human thrombogenesis.

We have investigated the potential use of perfusion techniques in the evaluation of the thrombogenic profile of factor IX concentrates. Blood from healthy donors was anticoagulated with low molecular weight heparin and incubated with one of the following: (a) diluent (DIL); (b) a prothrombin complex concentrate (PCC); (c) an intermediate-purity concentrate (FIX/X); or (d) a high-purity concentrate (HPFIX). The thrombogenic potential was assessed as: (1) fibrin formation on subendothelium (Baumgartner's perfusion) and (2) prothrombin activation fragment 1+2 (F1+2, nM) determination. The percentage of fibrin deposition on the subendothelium was only significantly increased after incubation with PCC (62.0+/-3.6% vs. DIL 35.0+/-6.1%;p<0.05). None of the FIX concentrates modified platelet interaction versus control blood (DIL: 26.7+/-2.1%). F1+2 baseline values in anticoagulated blood were 0.6+/-0.1 nM. Preperfusion levels of F1+2 reached values of 4.4+/-0.1 nM for PCC and 5.4+/-0.1 nM for FIX/X. After perfusion, F1+2 values were 2.7+/-0.2 nM for DIL, 5.6+/-0.1 nM for PCC and FIX/X, and 3.3+/-0.2 nM for HPFIX. While measurement of F1+2 was influenced by residual contaminants present in the concentrates, the morphometric evaluation of fibrin deposition on perfused vascular surfaces could be more closely related to the net thrombogenic profile of each FIX preparation.

Animals↗
PubMed1997

Decreased whole blood factor IX activity following hemodilution with hemoglobin A-zero in-vitro.

Previous studies of hemoglobin-based oxygen carriers and their effects on coagulation have shown conflicting results. This study re-examined the effect of hemoglobin solution on blood coagulation in whole blood using highly purified human hemoglobin Ao (HbAo). Citrated human whole blood samples were diluted 1:1 with HbAo (7gHb/dl) or human serum albumin (HSA; 5g/dl) as a protein control, and both activated partial thromboplastin time (aPTT) and prothrombin time (PT) were measured using a mechanically based whole blood coagulometer. Multiple runs were performed with the same volunteer donor sample. The mean aPTT time of HbAo-diluted samples (105.9 +/- 19.9 sec., n = 41) was significantly longer than the undiluted controls (46.4 +/- 5.6 sec., n = 54) or HSA-diluted blood (77.1 +/- 12.7 sec., n = 41) indicating an abnormal intrinsic coagulation pathway. There was no significant difference between the PT times of the HbAo and HSA-diluted samples. To examine the cause of the prolonged aPTT times with HbAo dilution, we performed activity assays of intrinsic factors XII, XI, IX, and VIII in a citrated human whole blood system diluted 1/5 and 1/10 with normal saline solution (NSS), and then 1:1 with either HbAo, HSA, or NSS. Only the Factor IX activity was significantly depressed by hemodilution (1/5 HbAo 50.20 +/- 8.11; HSA 61.05 +/- 6.72; NSS 74.75 +/- 9.83. 1/10 HbAo 46.50 +/- 5.57; HSA 64.97 +/- 11.01; NSS 67.92 +/- 16.03). These results suggest that in-vitro hemodilution with HbAo causes a hypocoagulatory response through interference with Factor IX function.

Blood Coagulation↗