Hereditary plasma thromboplastin antecedent (PTA,FXI)

A rare case of factor XI (PTA) deficiency was discovered in a Saudi family in the Riyadh area. Nine members of the family were studied. Two were found to have a severe PTA deficiency’ levels of factor XI clotting activity were 0.01 i.u./ml and 0.02 i.u./ml respectively. Both plasmas were markedly deficient in factor XI antigen and appeared to be negative for cross-reactive material (CRM-). The parents were first cousins and both were found to have a minor PTA deficiency. Factor XI levels were: mother 0.048 i.u./ml and father 0.33 i.u./ml. Another sibling was found to have a FXI level of 0.47 i.u./ml. Menorrhagia and bleeding for 1 day after tooth extraction were the main bleeding manifestations found in one member with severe PTA deficiency. Clinically this member presented with iron deficiency anaemia. Other family members had no significant history of bleeding tendency. This is the first report of a Saudi Arabian family with PTA deficiency.     

Hereditary plasma thromboplastin antecedent (PTA, FXI) deficiency in a Saudi family

A rare case of factor XI (PTA) deficiency was discovered in a Saudi family in the Riyadh area. Nine members of the family were studied. Two were found to have a severe PTA deficiency; levels of factor XI clotting activity were 0.01 i.u./ml and 0.02 i.u./ml respectively. Both plasmas were markedly deficient in factor XI antigen and appeared to be negative for cross-reactive material (CRM-). The parents were first cousins and both were found to have a minor PTA deficiency. Factor XI levels were: mother 0.048 i.u./ml and father 0.33 i.u./ml. Another sibling was found to have a FXI level of 0.47 i.u./ml. Menorrhagia and bleeding for 1 day after tooth extraction were the main bleeding manifestations found in one member with severe PTA deficiency. Clinically this member presented with iron deficiency anaemia. Other family members had no significant history of bleeding tendency. This is the first report of a Saudi Arabian family with PTA deficiency.     

Plasma thromboplastin antecedent (PTA) deficiency; clinical,coagulation, therapeutic and hereditary aspects of a new hemophilia-like disease

1. An analysis of the original PTA deficient family, including coagulationstudies performed upon 13 members comprising 4 generations, has been presented.

2. PTA deficiency is transmitted as an autosomal dominant trait with a probable high degree of penetrance and variable expression of the gene.

3. PTA deficiency can occur its varying degrees ranging from a severe formwith prolonged clotting time and markedly abnormal heparin clotting time andprothrombin utilization to a mild form manifesting a normal clotting time andslightly impaired prothrombin utiliztition.

4. Studies on the treatment of PTA deficiency reveal that the defect is corrected by the administration of stored plasma with the effect gradually disappearing over the period of one week.

5. Various properties of PTA are discussed and compared with AHG andPTC.

Submitted on April 27, 1954 Accepted on July 6, 1954     

A specific and sensitive radioimmunoassay for rat C-peptide

A sensitive and specific radioimmunoassay for rat serum C-peptide (RCP) has been developed and validated using a guinea pig anti-rat C-peptide antibody to synthetic rat C-peptide. Negligible crossreactivity (<0.01%) to human proinsulin was observed, whereas human insulin, human pancreatic polypeptide (hPP), porcine insulin, porcine C-peptide, bovine insulin, rat insulin, porcine-PP, and glucagon, respectively, did not produce measurable displacement of RCP tracer. Human C-peptide even in a supraphysiological concentration range crossreacted poorly (<0.1%). The sensitivity limit of the assay calculated at ±3 standard deviations was 24.2pM (0.07 ng/mL). RCP standard concentrations ranged from 25–1600pM. The intraassay-and between assay-coefficient of variations (CV) were 3.5–6.1% and 4.1–9.5%, respectively. The mean percentage recovery of RCP added to rat serum samples was 100.8±2%. Serum volume dilution from 25 to 100 μL did not significantly alter the expected RCP level. Migration of rat serum C-peptide and that of synthetic RCP were identical in a Sephadex G-50 chromatographic analysis. The mean fasting and postprandial plasma RCP levels in normal rats were 102±15pM and 485±75pM, respectively. RCP levels following intravenous glucose tolerance test in diabetic and nondiabetic rats were consistent with expected patterns. In conclusion, we have developed and validated a rat C-peptide assay that is sensitive, simple, and specific for RCP in serum. The assay provides a reliable tool for studies of diabetes using rodent animal models.     

Factor XI (plasma thromboplastin antecedent) deficiency in Ashkenazi Jews is a bleeding disorder that can result from three types of point mutations.

Factor XI (plasma thromboplastin antecedent) deficiency is a blood coagulation abnormality occurring in high frequency in Ashkenazi Jews. Three independent point mutations that result in a blood coagulation abnormality have been identified in the factor XI gene of six unrelated Ashkenazi patients. These mutations either disrupt normal mRNA splicing (type I), cause premature polypeptide termination (type II), or result in a specific amino acid substitution (type III). The three different genotypes were present in the six patients as type I/II, type II/III, and type III/III. Thus far no correlation was found between the three genotypes and the bleeding tendency in these patients.     

Interactions among Hageman factor, plasma prekallikrein, high molecular weight kininogen, and plasma thromboplastin antecedent.

To investigate the earliest steps of the intrinsic clotting pathway, Hageman factor (Factor XII) was exposed to Sephadex gels to which ellagic acid had been adsorbed; Hageman factor was then separated from the gels and studied in the fluid phase. Sephadex-ellagic acid-exposed Hageman factor, whether purified or in plasma, activated plasma thromboplastin antecedent, but only when high molecular weight kininogen was presnet. In the absence of plasma prekallikrein, maximal activation of plasma thromboplastin antecedent was slightly delayed in plasma, a delay not observed with similarly treated purified Hageman factor. Thus, high molecular weight kininogen was needed for expression of Hageman factor's clot-promoting properties and plasma prekallikrein played a minor role in the interaction of ellagic acid-treated Hageman factor and plasma thromboplastin antecedent.     

A sensitive and specific radioimmunoassay for arginine vasopressin and its validation

A sensitive and specific radioimmunoassay (RIA) for arginine vasopressin (AVP) has been developed and validated. Synthetic AVP was coupled to bovine serum albumin (BSA) with glutaraldehyde. Antisera against AVP were raised in three rabbits immunized with AVP-BSA complex. After 6 months, at the 16th injection, one of the antisera had a titer high enough to be utilizable for RIA at a final dilution of 1:400,000. The labeling of AVP with 125I Na was performed with the modified chloramine T method, and the purification of iodinated AVP was done with gel filtration chromatography on a Sephadex G-25 fine column (1 X 20 cm) with an elution buffer of 0.01 M acetic acid containing 0.1% BSA. Radioactivities from the Sephadex G-25 were eluted in three peaks. 125I-AVP, which was reactive to the antiserum, was contained in the third peak, and 125I-AVP in the fractions on the down slope of the peak was used for the radioligand in the amount of 1000 cpm. The specific activity of purified 125I-AVP was about 400 muCi/microgram. Diluted antiserum and samples, unlabeled AVP or related peptides were preincubated at 4 degrees C for 24 hr, and then 125I-AVP was added to the mixture and incubated for a further 72 hr. Separation of B and F was done with polyethyleneglycol. The minimal detection limit of AVP, which was 95% of the confidence limit of the mean value of B0, was 0.4 pg/tube. The cross-reactivities with lysine vasopressin, arginine vasotocin, DDAVP and oxytocin were 0.1%, 30%, 1% and 0%, respectively. AVP in plasma was extracted with cold acetone and petroleum ether. The recoveries of synthetic AVP from plasma which was added (2-16 pg) were more than 94%. The intra and inter-assay coefficients of variation determined by plasma of AVP concentration of about 4.8 pg/ml were 8.7% and 11.3%, respectively. The RIA detected AVP of concentration as low as 1 pg/ml following the extraction procedure. AVP immunoreactivity was detected without extraction in urine, and the lyophilized cerebrospinal fluid and acid extract of tissues of the central nervous system, and the reactivities in these samples were demonstrated to be immunologically identical to that of synthetic AVP when diluted serially. The changes of plasma and urinary AVP concentration on water intake, water deprivation and smoking in humans were clearly demonstrated.(ABSTRACT TRUNCATED AT 400 WORDS)     

Amidolytic assay of human factor XI in plasma: comparison with a coagulant assay and a new rapid radioimmunoassay

The traditional coagulant assay for plasma factor XI suffers from a relatively high coefficient of variation, the need for rare congenitally deficient plasma, and a poor correlation between precision and sensitivity. We have developed a simple functional amidolytic assay for factor XI in plasma using the chromogenic substrate PyrGlu-Pro-Arg- p-nitroanilide (S-2366). After inactivation of alpha 1-antitrypsin, CI inhibitor, and other plasma protease inhibitors with CHCI3, plasma was incubated with kaolin, in the absence of added calcium, which limited the enzymes formed to those dependent on contact activation. Soybean trypsin inhibitor was used to minimize the action of kallikrein on the substrate. Once the reaction was complete, corn trypsin inhibitor was used to inactive factor XIIa, the enzyme generated by exposure of plasma to negatively charged surfaces, which had activated the factor XI. The assay is highly specific for factor XI, since plasma totally deficient in that zymogen yielded only 1%-3% of the enzymatic activity in normal plasma under identical conditions. The requirements for complete conversion of factor XI to XIa in plasma within 60 min were, respectively, factor XII, 0.6 U/ml, and high molecular weight kininogen, 0.2 U/ml. Prekallikrein was not an absolute requirement for complete activation but did accelerate the reaction. The intraassay coefficient of variation was 3.4%, and the mean of 35 normal plasmas was 1.00 U +/- 0.24 SD. In addition, a new rapid radioimmunoassay was devised using staphylococcal protein A as the precipitating agent for a complex of factor XI antigen with monospecific rabbit antibody. The mean was 1.01 U +/- 0.30 SD. The correlation coefficients for amidolytic versus coagulant and amidolytic versus radioimmunoassay were r = 0.95 for the former and 0.96 for the latter. Thus, a simple, accurate amidolytic assay and a radioimmunoassay have been devised for measuring factor XI in plasma that correlate well with the coagulant activity of factor XI, as determined in our laboratory.     

Assay of Plasma Thromboplastin Antecedent (PTA) with Artificially Depleted Normal Plasma

Plasma artificially depleted of PTA by incubation following activation withdiatomaceous silica was evaluated as a reagent for the assay of PTA. It gaveresults which were comparable to those obtained with naturally deficient plasma and had the advantages of being readily available and more stable onstorage. Laboratory differentiation was possible between PTA and HF deficiency.

Submitted on December 20, 1962 Accepted on March 1, 1963     

Studies on a circulating anticoagulant in systemic lupus erythematosus: evidence for inhibition of the function of activated plasma thromboplastin antecedent (factor XIa).

Plasma proteins which interfere with blood coagulation have often been described in patients with systemic lupus erythematosus (SLE). The most frequent type interferes with the conversion of prothrombin to thrombin and thus prolongs the prothrombin time. Infrequently, SLE patients exhibit anticoagulants which appear to block the earlier stages of coagulation such as those involving factor VIII or the formation of activated factor XI (factor XIa). The anticoagulant reported here was studied by means of a sequential clotting system utilizing crude coagulation factors and was noted to interfere with the action of activated plasma thromboplastin antecedent (PTA) during the activation of factor IX. This anticoagulant was found in gamma-globulin-rich ethanol fractions of plasma. After gel filtration, it was found principally in fractions containing IgM globulins but also, to a lesser extent, in IgG-rich fractions. In this respect, it is similar to anticoagulants reported in certain other cases of SLE. Attempts to confirm the immunoglobulin nature of the anticoagulant by immunoabsorption were, however, inconclusive