Protein C (PC) is a vitamin K-dependent protein which functions as both an anticoagulant and profibrinolytic. It is synthesized as a single chain protein (SC-PC) and post-translationally modified ...into a two chain form (2C-PC). Two chain PC consists of a light chain (LC) and a heavy chain (HC). The present study was undertaken to determine the composition of the molecular forms of PC in plasma. PC was immunoprecipitated, subjected to SDS-PAGE and Western blotting. The blots were scanned by densitometry to determine the distribution of the various forms. The percentage of SC-PC and 2C-PC was found to be 10% and 90% respectively. This is in agreement with previous work. SC-PC and the heavy chain of 2C-PC consisted of three molecular forms ("alpha", "beta", and "gamma"). The "alpha" form of HC is the standard 2C form with a MW of 40 Kd. The "beta" form of HC has also been described and has MW which is 4 Kd less than the "alpha" form. The "gamma" species of the SC and 2C-PC has not been previously described. However, its 3 Kd difference from the "beta" form could be due to modification of the "beta" species or to a separate modification of the alpha-HC. The LC of PC was shown to exist in two forms (termed form 1 and form 2). The difference between these two forms is unknown. The molecular forms of PC are most likely due to a post-translational modification (either loss of a carbohydrate or a peptide) rather than from plasma derived degradation.
Heparin cofactor II (HC II) was measured by a chromogenic activity assay in normal preterm infants (gestational age, 28-36 weeks; n = 17; 29% +/- 11.5 mean +/- 1 SD, range 11-51), normal full-term ...infants (n = 18; 49% +/- 6.6 mean +/- 1 SD, range 36-58), and normal adults (n = 38; 101% +/- 14 mean +/- 1 SD, range 73-130). Normal children attained adult levels at approximately 5 to 7 months of age. The lower values in preterm and term infants most likely reflect immature liver function. Neither adults and children with a history of thrombosis with prior negative evaluation (n = 74), patients with documented protein C and protein S deficiency (n = 4), nor sick infants without evidence of consumptive coagulopathy (n = 15) had significantly lower levels of HC II activity. Infants with disseminated intravascular coagulation (n = 2) had strikingly lower levels of HC II activity.
To review the role of acquired and inherited prothrombotic risk factors that increase the risk of thrombosis in oral contraceptive users, during pregnancy, and in neonates, infants, and children; and ...to determine by the consensus opinion of recognized experts in the field which risk factors should be determined in which individuals at which time.
Review of the medical literature and current clinical practice by a panel of experts in the field of thrombophilia.
The experts made an extensive review of the published literature and prepared a draft manuscript, which included preliminary recommendations. The draft manuscript was circulated to participants in the College of American Pathologists Conference XXXVI: Diagnostic Issues in Thrombophilia prior to the conference. The manuscript and recommendations were then presented at the conference for discussion. Recommendations were accepted if a consensus of the 26 experts attending the conference was reached. The results of the discussion were used to revise the manuscript into its final form.
This report reviews the options for testing for thrombophilic states in women using oral contraceptives, during pregnancy, and in neonates and children. General guidelines for testing in these clinical situations are provided, along with citation of the appropriate supporting literature.
Hemophilia B is a sex-linked recessive bleeding disorder characterized by the presence of either a decreased amount of normal factor IX (FIX) or the presence of a dysfunctional FIX. We have ...identified a unique mutation in a family with mild hemophilia B. DNA analysis of family members revealed a single base transition in the 8th exon of the FIX gene predicting an amino acid change of Asn 346-->Asp in the catalytic domain. The FIX variant, named FIX Denver, was purified from proband plasma. Kinetic studies of factor X (FX) interactions with normal FIXa or FIXa Denver and phospholipid (PL) showed little difference in kcat but a significant difference when factor VIIIa (FVIIIa) was included in the reaction. Using kinetic assays to infer the Kd of FIXa for FVIIIa, normal FIXa had a Kd of 0.095 nM while that of FIXa Denver was 9.85 nM. The major defect caused by this point mutation is a marked decrease in the affinity of FIXa Denver for factor VIIIa.
Patient‐reported outcome (PRO) measures have been used to assess quality of life and health state preferences from the patient’s perspective. However, they have not been fully utilized in haemophilia ...clinical practice and research. A series of meetings were convened to review and document the state of the art in PROs relevant to haemophilia. Experts developed a process for selection of measures and identified published measures of health‐related quality of life (HRQoL) relevant to patients with haemophilia. These were synthesized and reviewed. Patient preference measures were also identified and reviewed. Although the majority of measures were developed for and validated in adults, several measures were identified for use in paediatric populations. This paper recommends an approach to the selection of PROs for application in haemophilia clinical research and practice and identifies several potential measures relevant for application in haemophilia clinical research and practice.
Dysprothrombinaemia is a rare, congenital cause of bleeding. Fewer than 25 families who express a functional prothrombin (factor II) defect have been reported. The original patient with prothrombin ...Denver had a severe haemophilia‐like bleeding disorder treated with weekly prophylactic factor replacement. Analysis of factor II activity and antigen in the patient showed a factor II activity of 5 units/dl and factor II antigen of 21 units/dl. Genomic DNA from the patient, mother and brother was obtained from peripheral blood white cells. Oligonucleotides were constructed, and prothrombin exons were amplified via polymerase chain reaction (PCR). The entire sequence of the thrombin portion of the molecule (exons VIII–XIV) and that of exons I–II and IV–VII was determined. This moderately severe dysprothrombinaemia was found to be associated with compound heterozygosity for two different Glu→Lys point mutations, at amino acid positions 300 and 309. Assays of plasma from the prothrombin Denver proband suggested that the functional defect was in the activation of zymogen to enzyme.
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