Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.6 (thromboplastin)
 13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Studies of the clotting mechanisms in the plasma of a Burmese python (Python molurus bivittatus) confirm earlier information that both extrinsic and intrinsic pathways of thrombin formation participate in reptilian hemostasis. Plasma fibrinogen was present at a concentration comparable to that in human plasma. Other assays were hampered by the need to use nonreptilian reagents. The activated partial thromboplastin time was shorter than was that of human plasma, thus implying the presence of prothrombin in python plasma; however, this protein could be demonstrated only in trace amounts. Similarly, only small amounts of Hageman factor (factor XII) and antihemophilic factor (factor VIII) were detected, and none of plasma prekallikrein, high-molecular-weight kininogen, and Christmas factor (factor IX). The prothrombin time was slower than that of human plasma. Factor VII was not detected, but both proaccelerin (factor V) and Stuart factor (factor X) were present. Python plasma inhibited bovine thrombin and human plasmin, but it was deficient in fibrinolytic capacity.
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PMID:Notes on clotting in a Burmese python (Python molurus bivittatus). 234 66

Normal newborn infants have a prolonged partial thromboplastin time compared to that of older infants or adults. This finding has been related to combined deficiencies of multiple clotting factors, with the exception of proaccelerin (factor V) and antihemophilic factor (factor VIII). The present study confirms the presence of decreased titers of Hageman factor (HF, factor XII), plasma prekallikrein, and high molecular weight kininogen during the neonatal period, as demonstrated in clotting assays; the degree of these relative deficiencies is usually such that only the low titer of HF appears to contribute significantly to the abnormally long PTT. Additionally, procoagulant titers of HF and plasma prekallikrein were relatively lower than the concentration of these factors determined immunologically. The mechanisms underlying this phenomenon are not known.
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PMID:Studies on some coagulation factors (Hageman factor, plasma prekallikrein, and high molecular weight kininogen) in the normal newborn. 743 82

Factor V (FV; proaccelerin or labile factor) is the plasma cofactor for the prothrombinase complex that activates prothrombin to thrombin. FV deficiency can be caused by mutations in the FV gene or in genes encoding components of a putative cargo receptor that transports FV (and factor VIII) from the endoplasmic reticulum to the Golgi. Because FV is present in platelet alpha-granules as well as in plasma, low FV levels are also seen in disorders of platelet granules. Additionally, acquired FV deficiencies can occur in the setting of rheumatologic disorders, malignancies, and antibiotic use and, most frequently, with the use of topical bovine thrombin. FV levels have limited correlation with the risk of bleeding, but overall, FV-deficient patients appear to have a less severe phenotype than patients with haemophilia A or B. The most commonly reported symptoms are bleeding from mucosal surfaces and postoperative haemorrhage. However, haemarthroses and intramuscular and intracranial haemorrhages can also occur. Because no FV-specific concentrate is available, fresh frozen plasma remains the mainstay of treatment. Antifibrinolytics can also provide benefit, especially for mucosal bleeding. In refractory cases, or for patients with inhibitors, prothrombin complex concentrates, recombinant activated FVIIa, and platelet transfusions have been successfully used. Some patients with inhibitors may also require immunosuppression.
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PMID:Factor V deficiency: a concise review. 1914 Nov 56

The clotting factor V, also known as proaccelerin or labile factor, is synthesized by the liver and possibly by the megakaryocytes. Factor V exerts a pivotal role in hemostasis, as it participates in both procoagulant and anticoagulant pathways, being an essential cofactor of the prothrombinase complex in the former case and participating in the inactivation of factor VIII (FVIII) in the latter. Isolated factor V deficiency due to mutations in the F5 gene is a rare inherited coagulopathy typically associated with a broad spectrum of bleeding symptoms, ranging from easy bruising, delayed bleeding after haemostatic challenges such as trauma or surgery to more severe joint bleeds. The combined deficiency of factor V and FVIII, commonly known as F5F8D, is a recessive disorder not attributable to the association of isolated factor V and FVIII deficiencies, but rather to defective intracellular processing of both proteins due to mutations involving the LMAN1 and MCFD2 genes, which encode two proteins forming an essential cargo receptor complex. Overall, patients affected by F5F8D do not bleed more in terms of both frequency and severity than those carrying specific deficiencies of both factors and the bleeding phenotype is generally mild. Although now increasingly rare, inhibitors directed against factor V may also develop in individuals of any age and are characterized by a very heterogeneous clinical phenotype. The aim of the current review is to provide an overview on the physiopathology, diagnostics, and clinical management of both inherited and acquired factor V deficiency.
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PMID:Inherited and acquired factor V deficiency. 2124 50