Owen, C. A.

SUMMARY Normative values were established for results of tests of blood coagulation and platelet function in swine. In swine that have von Willebrand's disease, bleeding time was prolonged, platelet retention was decreased glass bead column), and factor VIII concentration was low.

SUMMARY Factor VIII concentrations in plasma, platelet retention, and ear bleeding times were determined on 35 normal pigs, 40 obligate carriers of porcine von Willebrand's disease, and 25 bleeders. The bleeders could be distinguished from the normal pigs by each of the 3 tests. At most, only one-third of the carriers could be distinguished from the normal pigs by any one test. A hemostatic score, derived from the results of the 3 tests, increased the discrimination to slightly more than half. The degrees of abnormality on the 3 diagnostic tests seemed to vary from family to family and might have been related to the sire of the bleeder.

SUMMARY Copper (Cu) was assayed in serial liver biopsy specimens of 5 pups resulting from a mating of 2 Bedlington Terrier carriers of inherited Cu toxicosis; the latter were sibling offspring of an affected Bedlington Terrier and a normal dog. Between 5 and 7 months of age, 1 of the pups had acceptable hepatic Cu values in each of 6 specimens. The hepatic concentration of Cu in another pup increased steadily from 801 to 3,874 μg/g dry weight. The other 3 pups may be heterozygotes (carriers); in 1—the hepatic Cu peaked at 1,043 μg/g at 9 months, in the 2nd—at 636 μg/g at 7 months, and in the 3rd—at 492 μg/g at 7 months. Acceptable concentrations were present in these 3 dogs at 9 to 14 months. Results in the present study indicate that heterozygotes may have 1 normal and 1 abnormal controller gene for regulating their hepatic Cu metabolism, thus accounting for the increased hepatic Cu concentration only in the early months of life. The affected Bedlington Terrier with 2 abnormal genes was unable to suppress the progressive hepatic accumulation of Cu. Paired liver biopsy specimens obtained at 5 to 7 months and at 14 or 15 months of age might distinguish the heterozygote from the normal and the affected Bedlington Terrier pups.

When isolated neonatal pig livers were perfused with blood from pigs with von Willebrand’s disease, no factor VIII coagulant activity (VIII:C) emerged in the perfusate. When purified porcine Willebrand factor, lacking VIII:C, was added to the perfusate it rapidly diminished, presumably being taken up by the liver. Concurrently VIII:C rose steadily in the blood during the 5 hours of perfusion. Similarly, isolated adult rat livers released no VIII:C when they were perfused with rat erythrocytes suspended in Tyrode’s solution containing 6% bovine serum albumin. VIII:C did emerge if cryoprecipitate from aged rat plasma were added. The neo-VIII:C was rapidly inactivated by plasma from a patient with classic hemophilia who had developed an antibody to VIII:C Addition of cycloheximide to the rat before extirpation of the liver, as well as to the perfusate, prevented the emergence of VIII:C. We suspect that VIII:C is derived from the liver but only when Willebrand factor is present.

An automated method for specific factor assays has been developed using a novel thrombin-specific chromogenic substrate (developed by A. Aiyappa, Ph. D., Abbott Labs). For factors VIII, IX, XI and XII, the test system includes an ellagic acid activator and brain phospholipid in a calcium containing tris buffer pH 7.4. These are mixed with a plasma sample consisting of a mixture of specific factor deficient substrate and test plasma for 5 minutes and then the chromogenic substrate is added. After another 5 minutes the increase in optical density ΔOD is recorded. Normal plasma serially diluted in specific factor deficient substrate is used to construct a standard graph and test plasma results are interpolated from this.Fifty-four comparative assays have been done for factors VIII and IX and correlated with the results obtained from conventional clotting assays. For factor VIII the correlation coefficient (r)=0.935 (N=35) and for factor IX r=0.941 (N=19). While insufficient data exists to date for factors XI and XII, these assays appear to be comparable to the VIII and IX results.The assays for factors V, VII and X use a simplified system in that the chromogenic substrate and phospholipid are added together. The ΔOD is again recorded after 5 minutes. Test plasma results are interpolated from a standard graph constructed using serially diluted normal plasma as before. To date only the factor V assay has enough data to do a correlation with the clotting assays and r=0.953 (N=13) which is similar to the r value for the VIII and IX assays.Because of the widespread availability of the automated analyzer used in the assay and the standardization of end point determination it provides, specific factor assays might be made more widely available outside specialized coagulation centers.

Measuring the release of small amounts of a clotting factor from an isolated perfused rat liver is difficult if the perfusate already contains some of the factor. Further, platelet-containing perfusates generate a coagulant activity that may invalidate clotting assays.We have successfully employed a completely synthetic blood substitute for rat liver perfusions. The perfusate is “Fluosol-43” generously furnished by Alpha Therapeutic Corporation. The oxygen-carrying perfluorochemical is FC-43 (perfluorotributylamine) and the substitute for albumin is hydroxyethyl starch. Using the Brauer perfusion technique, we found that rat livers in 5 hours released an average of 2.3% of the normal plasma concentration of prothrombin, 8.4% factor V, 16.2% factor VII, 7.0% factor IX, 3.7% factor X, 28.3% factor XI and 12.3% factor XII. Antithrombin III and plasminogen were also generated.Only minute amounts of factor VIII were released unless serum, cryoprecipitate or cryoprecipitate-free plasma was added; then the yield was 8.8% on average. The more “venom factor” (platelet aggregability with Bothrops alternata venom) added to the synthetic perfusate, the more factor VIII was released.

Abstract Von Willebrand pigs have all the manifestations of the severe human disease. The role of Willebrand antigen (VIII R:AG) and ristocetin cofactor (VIII: RWF) was assessed in these pigs by (1) transfusion and (2) ’in vitro' bleeding time assay. The skin bleeding time became normal when the level of transfused Willebrand factor (VIII R: AG/RWF) was raised in the plasma above 30 U/dl. After single or repeated transfusions, skin capillary endothelium and platelets were still distinguished from normal by VIII R:AG deficiency. When incisions in excised porcine skin (’in vitro' bleeding time) were perfused with blood and plasma fractions, haemostasis occurred when plasmatic Willebrand factor exceeded 30 U/dl whether the skin or platelets came from normal or from von Willebrand pigs. The platelet plug occluding the skin incision contained VIII R:AG by immunofluorescence. Willebrand factor appears to coat surfaces and to serve as a platelet attachment protein. These bleeder pigs are resistant to atherosclerosis. If platelets are involved in early atheroscolerotic lesions, the role of Willebrand factor in platelet - blood vessel interaction may be important.