Plasma Factor Activity Research Articles

Ristocetin-Willebrand factor activity in dog plasma.

A sensitive and reproducible method for the quantitation of ristocetin-Willebrand factor activity in canine plasma is described. This assay measures the initial velocity of aggregation of suspensions of canine washed platelets in the presence of ristocetin and ristocetin-Willebrand factor. The washed platelets are stable for 4 h and when prepared from the same donor vary little in their day-to-day response to ristocetin. The calculated mean plasma ristocetin-Willebrand factor activity in 37 normal dogs using this method is 98 +/- 26% (mean +/- SD) Ristocetin-Willebrand activity is 106 +/- 25% in dogs with severe hemophilia A and 45 +/- 13% in dogs with moderate forms of von Willebrand's disease.

Synthesis of factor VIII antigen by cultured guinea pig megakaryocytes.

Immunoprecipitates containing guinea pig Factor VIII antigen were prepared from guinea pig plasma with a cross-reacting rabbit anti-human Factor VIII. Monospecific antisera to guinea pig Factor VIII antigen were produced in rabbits by using these washed immunoprecipitates as immunogens. The resulting antisera to guinea pig Factor VIII antigen detected Factor VIII antigen in guinea pig plasma and inhibited the von Willebrand factor activity in guinea pig plasma. This antibody also detected Factor VIII antigen in a solubilized protein mixture prepared from isolated cultured guinea pig megakaryocytes. Cultured guinea pig megakaryocytes were labeled with radio-active leucine. By radioautography, 96.2% of the radio-activity was present in megakaryocytes. The radio-active Factor VIII antigen present in the solubilized cell protein mixture was isolated by immunoprecipitation and characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The results demonstrate that cultured guinea pig megakaryocytes synthesize Factor VIII antigen which contains the same polypeptide subunit (mol wt 200,000) present in guinea pig plasma Factor VIII antigen.

Correlation of platelet aggregation, plasma factor activity, and megathrombocytes in diabetic subjects with and without vascular disease

Second-phase platelet aggregation induced by adenosine diphosphate (ADP) and epinephrine was measured in fasting platelet-rich plasma in normals, “prediabetics”, and diabetics with or without vascular disease. “Plasma factor” potentiation of ADP-induced second-phase platelet aggregation was also estimated, as were megathrombocyte numbers in the same patient groups. There was an increased sensitivity of second-phase platelet aggregation noted with both aggregating agents in all diabetic groups except for the prediabetics. This activity was paralleled by an increase in plasma factor activity. In vivo evidence of an increased turnover of platelets in frank diabetics was suggested by increased numbers of megathrombocytes. These studies demonstrate that platelets from diabetics are sensitive to aggregating agents and that this sensitivity may be related to plasma factor(s) present in diabetics. In vivo platelet aggregation may be present in diabetics. Longitudinal studies will be necessary to establish the relationship of these findings to the genesis of diabetic vascular disease.

Corticotropin releasing factor (CRF) activity in rat plasma.

The ACTH-releasing activity of hypothalamic extract and rat plasma was examined with the dispersed rat pituitary cell technique of Swallow and Sayer (8). Although both plasma and serum caused ACTH release which was dose-related, stress did not enhance the ACTH releasing activity. Furthermore, separation studies of plasma using ultrafiltration and gel separation suggest that the CRF activity in plasma is associated with molecules of a molecular weight greater than 15,000.

The effect of calcium ions on the properties of factor IX and its activated form.

Summary. The activation of bovine plasma factor IX requires activated factor XI and calcium ions, but not phospholipids. It results in an apparent reduction in molecular size or shape as shown by gel filtration on Sephadex G‐200 and sucrose gradient ultracentrifugation. DEAE chromatography reveals that the surface charge may be altered upon activation. In the presence of calcium ions, both the precursor and activated form of factor IX showed reduction in sizes. Calcium ions also promote the adsorption of factor IXa on a glass surface. The significance of the change of size and surface charge in the interaction of factor IX and phospholipids is discussed.

Relationship of Blood Transfusions to Appearance of Mixed Leukocyte Culture Blocking Factor Activity in Plasma of Uraemic Patients and Renal Allograft Recipients

Plasma samples from haemodialysis patients, renal allograft recipients and haemophiliacs were studied for the presence of mixed leukocyte culture blocking factor activity (BFA). A history of blood transfusions received within the preceding 6 months of testing was significantly and directly correlated with the appearance and persistence of BFA in the plasma of haemodialysis patients. This association was not found in renal allograft recipients. The development of BFA was found to be associated with formation of lymphocytotoxins but not haemagglutinins. The authors have also demonstrated that BFA resides in the IgG fractions of serum samples obtained from both chronic uraemics undergoing haemodialysis and patients bearing renal allografts. BFA may play a minor role in the acceptance of human renal allografts.

Deficiency of fibrin stabilizing factor: report of a case, probably congenital, with observations on the effects of treatment with -aminocaproic acid and with prednisone.

A case of mild deficiency of fibrin stabilizing factor, probably congenital, is reported. Treatment with eaminocaproic acid and prednisone allowed bloodless dental surgery and, under controlled conditions, induced a temporary increase of fibrin stabilizing factor activity in plasma which paralleled a decrease in plasmin activity.

Clotting factor activity in cryoprecipitates and supernatant plasma prepared from blood collected into ACD, ACD-adenine, CPD, and CPD-adenine and from plasma collected by plasmapheresis.

Adenine has been used to prolong the survival of stored erythrocytes, and thus extend the storage period of blood. It seemed desirable to investigate the effect of this additive on the procoagulants of plasma that full use of cryoprecipitates and other plasma fractions could be made from blood drawn into an adenine‐enriched anticoagulant. Eight units of whole blood were drawn into each of four anticoagulants: ACD, ACD‐adenine, CPD, and CPD‐adenine. Cryoprecipitates were prepared from each unit of fresh plasma according to a modification of Pool's method. Assays for fibrinogen, prothrombin, and factors V, VII, VIII, IX, and X were performed on the cryoprecipitates and on the supernatant plasma drawn off the cryoprecipitates. Adenine did not alter the expected yield of factor VIII (AHF) in the cryoprecipitate. There was slight to moderate loss of factor V and fibrinogen, respectively, in the supernatant plasma, but prothrombin and factors VII, IX, and X were unaffected by the procedure. Assays also revealed good AHF activity in each unit of plasma from a double plasmapheresis; therefore, both units are satisfactory for use in preparing cryoprecipitates.

PSH-releasing factor activity in plasma of rats after hypophysectomy and continuous light.

Comparison of plasma from adult male hypophysectomized rats (1 and 2 months after surgery) with plasma from intact male rats for FSH-releasing activity showed that only plasma from the former induced release of FSH upon incubation with rat pituitary. When male rat pituitary was incubated with plasma from intact rats or with medium 199, no significant FSH release was observed in either group. FSH activity was not detected in plasma of intact or hypophysectomized rats when injected into assay rats, indicating that the FSH-releasing activity was not FSH. Exposure of hypophysectomized rats to constant light for 3 weeks increased FSH-releasing activity in the plasma to levels greater than found after hypophysectomy alone. Assays of hypothalamic FSH-RF content in intact, hypophysectomized, and hypophysectomized rats exposed to constant illumination showed no significant differences between any of these groups. These results suggest that hypophysectomy and constant light stimulate release of FSH-RF from the hypo...

Enzymatic release of folate activity from the red cells in megaloblastic anaemia of pregnancy.

The content of folate activity precursors in washed red cells and the enzymatic plasma factor activity, necessary for the release of folate from the precursors, were studied in normal subjects and in patients with megaloblastic anaemia of pregnancy. Subjects with megaloblastic anaemia of pregnancy had a significantly reduced folate activity precursor content, and 14 subjects (58%) had significantly low plasma factor activity, which in at least four subjects may have been due to the presence of inhibitors. This study indicates that impaired activity of the plasma factor may play a part in the aetiology of megaloblastic anaemia of pregnancy.

Thrombogenic Properties of Surface Factor; Evidence for an Anti-Surface Factor Activity in Canine Plasma.

SummaryPurified surface factor (SF or activation product) was prepared from canine plasma and its effect was studied on 22 dogs. It was shown that intravenous injection of SF increased the coagulability of the circulating blood (in vitro tests) and induced thrombosis in areas of vascular stasis (in vivo assay). The hypercoagulability was associated with the injected SF preparation and with no other known clotting factor increase. A second injection performed 61 minutes after the first was less effective. The survival period of injected SF seemed to be relatively short. This might be attributable, in part, to an inhibitory mechanism acting against SF (anti-SF) in plasma. Experimental evidence of the existence of such an inhibitor and its “progressive” mode of action is provided. Anti-SF has a variable titer normally, but appears to increase after the intravenous SF injection in dogs.