E.J.W. Bowie

Increased von Willebrand factor in diabetes mellitus.

Abnormal platelet function may play a role in the genesis of vascular complications in diabetes mellitus. We measured plasma levels of ristocetin-Willebrand factor and factor VIII antigen in 75 subjects and also measured aggregation-enhancing factor in subsets. We found increased levels of ristocetin-Willebrand factor in all groups of diabetics studied, even in mild diabetics free of vascular disease. Factor VIII antigen was increased only in diabetics with vascular disease. We could not find an aggregation-enhancing factor in any group.

Factor VIII (Willebrand) antigen and ristocetin-Willebrand factor in pigs with von Willebrand's disease.

Abstract The Willebrand antigen and the ristocetin-Willebrand factor were virtually undetectable in pigs with a severe form of von Willebrands disease. These findings establish that porcine von Willebrands disease is essentially the same as the human counterpart. The Willebrand antigen and ristocetin-Willebrand factor were reduced approximately 60% in pigs which are heterozygous. Furthermore these two new tests can be done on capillary blood, permitting earlier identification of the disease.

Prothrombin, thrombin and prothrombin fragments in plasma of normal individuals and of patients with laboratory evidence of disseminated intravascular coagulation

Abstract With specific immunoassays for prothrombin, thrombin-anti-thrombin-III complex and for prethrombin-1 antigen, we measured the levels of these proteins in the plasma of normal individuals and patients suspected of having chronic disseminated intravascular coagulation (DIC). The normal level of prothrombin in plasma was found to be 110–212 mg/liter, and of thrombin-anti-thrombin-III complex and prethrombin-1 antigen approximately 1 μg/ml. In patients with suspected DIC, prothrombin levels, as measured by immunoassay and two-stage clotting assay, were decreased in 14 of 19 studied. Levels of thrombin-anti-thrombin-III complex were normal in all the patients and those of prethrombin-1 elevated in only two of 19. The lack of elevation of these products is probably due to the small amount of prothrombin activated in these patients. Decreased synthesis may account for the low levels of prothrombin observed in some. Measurement of the level of these products of prothrombin is therefore not useful in the diagnosis and management of patients with DIC.

Platelet consumption in chronically induced plasma platelet factor 4-like activity reflecting rate of intravascular coagulation in dogs

Abstract Chronic intravascular coagulation was produced in eight dogs by continuous intravenous infusion of dog brain thromboplastin for 3 days to 18 days. About the third day of infusion there was a decrease in platelet count to 32% of the original value and an increase in plasma platelet factor 4-like (PF4-like) activity to 65% of the entire releasable PF4 of circulating platelets. These platelets released about twice the normal amount of PF4-like activity when aggregated in vitro with ADP. Turnover ( 51 Cr-labeled) was 2 times faster than normal. The level of plasma PF4-like activity seems to reflect the rate of platelet consumption in intravascular coagulation and provides information about platelet kinetics.

Stability of porcine factor VIII.

Abstract Citrated porcine plasmas, when incubated at 37°, lose their factor VIII activity as a function of time. This loss of activity is a first order process and the half-life of the factor VIII activity from von Willebrand (vWd) pigs (∼6 h) is shorter than the half-life of factor VIII from normals (∼ 14 h). After stimulation of a vWd pig by transfusion a factor VIII activity is found with an extremely short half-life (∼ 2.5 h). Carriers of porcine vWd disease have both a labile and stable fraction of factor VIII.

Hemostatic Effect of Transfused Willebrand Factor in Porcine von Willebrand’s Disease

Cryoprecipitate was infused into pigs with severe von Willebrands disease, and the bleeding time was corrected when the plasmatic level of VIII R:AG (WF) was above 30 U/dl. The VIII R:AG (WF) was not completely recovered but none was found in the plasma or endothelial cells. A new method for measuring the bleeding time is described--the ratio bleeding time. These results in pigs are compared with the reported results in humans.

Generation of plasmatic coagulation factors by the isolated rat liver perfused with completely synthetic blood substitute

Abstract Perfusion of isolated rat livers with a synthetic blood substitute (perfluorochemical with hydroxyethyl starch) indicated that these livers generate factors II, V, VII, IX, X, XI, XII, antithrombin III and plasminogen just as well as when they are perfused with blood components. Again it was demonstrated that rat livers release appreciable amounts of factor VIII:C only when exposed to some ingredient in plasma and serum, possibly VIIIR:AG.

Transfusion and autotransfusion of plasma in von Willebrand's disease☆

Abstract A patient with von Willebrands disease was transfused with a small amount of fresh frozen plasma. Factor VIII coagulant activity reached a peak at the 6th hour after transfusion whereas the factor VIII-related antigen peaked at the 3rd hour and started to decline rapidly. The ristocetin-Willebrand factor rose immediately after the transfusion to a level which would have been predicted from the amount of this activity transfused and remained at levels slightly lower than this for the remainder of the study. Transfusion of the patients own plasma obtained at the height of the factor VIII response produced no increase in any of the activities measured. Factor VIII stimulated by transfusion is more labile in vitro than normal Factor VIII.

Clinical evaluation of a new test of hemostasis: The filter bleeding time

The clinical value of a new in vitro test of hemostasis, which we have called Filter Bleeding Time (FBT), was determined in 59 patients referred because of a suspected bleeding disorder. FBT is based on the progressive slowing of the drop rate of citrated blood through a filter of woven Dacron under constant pressure as platelet aggregates occlude the filter. The value for FBT is defined as the time when the blood drop interval has reached 1 minute. The Mayo modification of the Ivy bleeding time (IBT) was performed in all patients; platelet response to ADP, collagen, epinephrine and arachidonate was performed in 24 patients. In 30 normal volunteers FBT measured 1-3 hr after venipuncture was 2.8 +/- 1.5 (means +/- 1SD) min. The FBT was prolonged in 3 of 3 patients with Glanzmanns thrombasthenia, 2 with disseminated intravascular coagulation, 1 with chronic lymphocytic leukemia, 1 with myelofibrosis, and 1 who had taken aspirin. In 6 patients FBT was prolonged while IBT was normal: 4 after taking aspirin, 2 with polycythemia vera. All 6 had reduced platelet aggregation (PA) to ADP (5 microM), collagen (2 mg/ml), epinephrine (5 microM) and/or arachidonate (1.7 mM). In 3 patients FBT was normal while IBT was abnormal: 1 with disseminated intravascular coagulation, 2 undiagnosed; 1 of these 3 had abnormal PA. Of 6 patients with von Willebrands disease, FBT was prolonged in 5 and borderline in 1; IBT was prolonged in 3, normal in 1, and not done in 2 infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of Platelets with the Endothelium in Normal and von Willebrand Pigs

In order to evaluate the possible role of platelets in the development of atherosclerosis, the aortas of 11 control pigs and 11 homozygous von Willebrand (vWD) pigs were examined for spontaneous atherosclerosis. Of the 11 normal pigs, six showed multiple atherosclerotic plaques with an intimal thickening of 63 to 130 µm. In contrast, none of the von Willebrand pigs had multiple plaques and only one showed a single lesion of more than 2 mm in diameter.