Von Willebrand's disease in pigs and atherosclerosis

There is experimental evidence that platelets, by interacting with the arterial wall may be important in the initiation of atherosclerosis. This paper describes the results of consecutive experiments indicating that pigs with impaired platelet-blood vessel interaction in the form of von Willebrand's disease are resistant to the development of atherosclerotic plaques. Ongoing experiments in these pigs are providing significant insight into the relationship of the circulating platelets, the endothelial cell and circulating von Willebrand factor, and the reactivity of the arterial wall in the process of atherosclerosis.

Problems of diagnosis of disseminated intravascular coagulation (DIC)

Acute generalized intravascular coagulation is regularly associated with fibrinolysis. Evidence of the clotting process includes thrombocytopenia, hypofibrinogenemia, prolongation of the prothrombin time (deficiency of factor V and fibrinogen) and of the partial thromboplastin time (factor VIII is also deficient). Evidence of fibrinolysis is elevation of fibrinolytic split products (FSP or FDP). A positive protamine gel results from both coagulation and fibrinolysis.

Surgical hemostasis

Every surgical procedure taxes the hemostatic defenses of the patient. If his hemostatic mechanism is sound, he is unlikely to have a bleeding problem during or after an operation, unless, of course, a suture or clip slips off. Two classes of patients do present bleeding problems to the surgeon. One group has a pre-existing bleeding tendency, the other acquires it during or after the operation. The recognition of patients with severe hemostatic disabilities, such as hemophilia, presents no problem since the patient is aware of the disease. The mild bleeder is less likely to be detected by screening tests than by adroit questioning. The major hemostatic defect that may develop during an operation, or shortly thereafter, is disseminated intravascular coagulation. This syndrome, always secondary, may accompany shock, mismatched blood transfusion, septicemia, or extensive malignancy. Its prevention or early recongnition is much easier than treatment after circulating platelets and some coagulation factors have been consumed and fibrinolysis is destroying fibrin and fibrinogen.

Functional platelet defects and their laboratory evaluation

Primary diseases of platelet function include Glanzmann's thrombasthenia, hereditary platelet release abnormalities (storage pool disease and release defect), Bernard-Soulier giant platelet syndrome, and platelet factor 3 defects. Qualitative defects of platelets are associated with many diseases, notably of the liver and kidney, and with the use of many drugs, particularly aspirin.

Hypofibrinogenemia-dysfibrinogenemia and von Willebrand's disease in the same family

Two Puerto Rican families were studied. One family included a number of members with dysfibrinogenemia occasionally associated with hypofibrinogenemia. The second family had members with von Willebrand's disease. The two diseases merged in the proband's immediate family; the affected members of this family exhibited a mild bleeding disorder. Others in the two families had no obvious bleeding tendency.

Inheritance of porcine von Willbrand's disease: study of a kindred of over 700 pigs

A study of over 700 pigs affected with von Willebrand's disease suggests that the classic disease is transmitted as an autosomal recessive trait. Less clear is the genetic basis of inheritance of variant types of this disease produced by selective mating.

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.

The von Willebrand pig as a model for atherosclerosis research

In order to evaluate a possible role played by 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, 6 showed multiple atherosclerotic plaques with an intimal thickening of 63 to 130 micrometer. 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. In a prospective study 5 control pigs and 5 vWd pigs were given a high (2%) cholesterol diet from the age of 3 to 9 months. All of the controls developed atherosclerotic plaques. In 4 of the pigs the plaques exceeded 13% of the aortic surface with an intimal thickening of 50 to 390 micrometer. In contrast, only one of the vWd pigs developed atherosclerotic plaques which only involved 7% of the aortic surface. Most of the vWd pigs, however, developed non-atherosclerotic flat fatty lesions. These findings may be related to the impaired platelet arterial wall interaction in vWd. The vWd pigs seem to be an ideal model for atherosclerosis research.

Resistance to arteriosclerosis in pigs with von Willebrand's disease. Spontaneous and high cholesterol diet-induced arteriosclerosis

The aortas of 11 pigs (aged 1-3 yr) with homozygous von Willebrand's disease (vWd) were compared with those of 11 normal pigs of the same ages. Six of the controls exhibited multiple arteriosclerotic plaques with intimal thickening of 63-130 mum. In contrast, none of the pigs with vWd had multiple plaques, and only one had a lesion >2 mm in diameter. In a subsequent study, 3-mo-old pigs (11 controls and 7 with homozygous vWd) were placed on a 2% cholesterol diet for up to 6 mo. All of the controls developed arteriosclerotic plaques in the aorta, and in nine of the controls, at least 13% of the entire surface was involved. Intimal thickness ranged up to 390 mum. In contrast, four of the pigs with vWd did not develop such lesions, two developed arteriosclerotic lesions affecting 6 and 7% of the aortic surface, and the seventh had 13% of the aortic surface involved. Most of the pigs with vWd, however, developed flat fatty lesions in contrast to the normal pigs whether on the normal or the high cholesterol diet. There was blue staining of the flat fatty lesions when two pigs with vWd were injected with Evans blue dye antemortem. By electron microscopy, severe endothelial damage was apparent, but there was no intimal proliferation. The coincidence of the impaired platelet-arterial wall interaction and lack of arteriosclerosis in this bleeding disease is discussed.

Porcine Willebrand factor: a population of multimers

Purified porcine Willebrand factor was analyzed by agarose-sodium DodSO4 electrophoresis. Multiple forms of the protein were found in a series of increasing molecular weights. A molecular mass calibration curve was constructed with fibrinogen (3.4 X 10(5) daltons), IgM (1 X 10(6) daltons), and glutaraldehyde-crosslinked IgM polymers (2, 3, and 4 X 10(6) daltons). As measured by this procedure, the apparent molecular weight of Willebrand factor polymers ranged from 1.1 X 10(6) to 2.1 X 10(7). Each member of the series differed from one another by approximately 1.5 to 1.9 X 10(6) daltons, indicating that members of the series were polymers of 6-mers to 8-mers of the 2.3 X 10(5) dalton subunit. Various purification procedures, used to isolate Willebrand factor active in inducing platelet aggregation, were seen to fractionate the polymers, in part, on the basis of size. The same purification procedures, when applied to procine von Willebrand plasma, failed to yield protein of molecular weight greater than 1.1 X 10(6).

Rat coagulation factors V, VIII, XI, and XII: vitamin K dependent

When rats were given single or multiple doses of warfarin, the levels of prothrombin and factors VII, IX, and X were depressed, as expected. However, modest reductions of factors V, VIII, XI, and XII, but not of fibrinogen, also occurred. The levels of all eight factors promptly returned to normal when vitamin K1 was given. Warfarin-resistant rats had no depression of any of the eight factors. When vitamin K deficiency was induced by internal or external biliary fistula, factors II-VII-IX-X decreased sharply and factors V-VIII-XI-XII decreased modestly. Again, all depression were promptly reversed by vitamin K1. Isolated livers from warfarinized rats did not generate the classic vitamin K-dependent factors during 5 h of perfusion but did generate small amounts of factors V, XI, and XII, although less than normal. The isolated rat liver apparently does not generate factor VIII.

Fibrinolytic degradation products in urine of anticoagulated transplant patients

A study of the level of urinary fibrinolytic split products in 14 renal transplant patients who received oral anticoagulants postoperatively revealed a tendency toward increased levels of fibrinolytic split products that were temporally related to graft rejection. The amount of fibrinolytic split products in the urine was positively related to the severity of rejection as well as to the final status of the allograft. Thus, the urinary level of fibrinolytic split products, as determined by the latex-coated particle test, can be used as an indicator of the course of warfarin-anticoagulated patients after renal allografting.

Cultured aortic endothelial cells from pigs with von Willebrand disease: in vitro model for studying the molecular defect(s) of the disease

Aortic endothelial cells from normal pigs and pigs with von Willebrand disease have been established in long-term cultures. Both cultures appeared similar in terms of general growth characteristics, morphologic features and ultrastructure. Immunofluorescent staining of these cultures with chicken (or rabbit) antiporcine ristocetin-Willebrand factor sera (or IgG) resulted in extensive perinuclear staining of the cells in both cultures. Additionally, staining of semiconfluent cultures of normal cells for ristocetin-Willebrand factor revealed an extensive meshwork of distinct, immunologically identifiable ristocetin-Willebrand factor-containing filaments between cells. Immunoreactive material was considerably decreased and more diffuse between cells in semiconfluent cultures from affected pigs. Through immunocytochemical staining with peroxidase-coupled antiserum, the filaments (of indeterminate length) were found to have a diameter of approximately 300 A. Finally, washed porcine platelets interacted extensively with scrape-damaged cultures of affected endothelial cells. This interaction of platelets with damaged normal cultures was abolished by pretreatment of the cultures with rabbit antiporcine ristocetin-Willebrand factor IgG.

Purification of porcine and human ristocetin-Willebrand factor

A plasmatic component required for the ristocetin-induced aggregation of platelets has been purified from normal human and porcine plasma by gel filtration (4% agarose) and anion-exchange chromatography (DEAE cellulose). No factor VIII coagulant activity was found associated with the purified human or porcine component. Urea sodium dodecylsulfate electrophoretic analysis of the purified component of both species indicated that the apparent molecular weight with intact disulfides is in excess of 500,000; after disulfide reduction with 2-mercaptoethanol, single components with an apparent subunit molecular weight of 230,000 were observed. Purified porcine ristocetin-Willebrand factor (RWF) co-sedimented in sucrose gradients with the factor present in normal plasma. Amino acid analysis of both human and porcine RWF indicated that all normal amino acids are present, whereas amino sugars were undetected. However, lipid analysis indicated 1% to 2% lipids present, including monoglycerides, di- and tri-glycerides, cholesterol, cholesterol esters, some free fatty acids, and a trace of phospholipid. A single line of identity was observed between normal human plasma and purified human RWF when immunodiffusion plates were run with purified rabbit anti-human RWF immunoglobulins. Antisera raised against human and porcine RWF's do not inhibit the factor VIII coagulant activity of the homologous plasma, nor is "spontaneously occurring" human factor VIII inhibitor neutralized by the isolated material of either species.

Quantitative bleeding time (hemorrhagometry). A review

Accurately determining the amount of blood lost during bleeding time tests has been little exploited. Equipment is now available for measuring both the time and volume automatically--a technique called hemorrhagometry. This quantitative procedure has generated a number of interesting and unsuspected observations. Bleeding times lengthen and blood loss is exaggerated as the skin is cooled. This is particularly true of patients who have hemostatic defects, such as hemophilia A; Not only is the hemophiliac different from normal in this regard but, in Sutor's preliminary observations, the asymptomatic carrier of hemophilia A also seems to be distinguishable from the noncarrier on this basis. The test seems potentially useful in evaluating the effect of drugs on platelet function and in assessing mild bleeding diatheses. Variations induced by either warming or cooling the skin may well have clinical applicability.

Generation of coagulation factors V, XI, and XII by the isolated rat liver

When isolated rat livers were perfused with platelet-free erythrocytes suspended in Tyrode's solution containing 6% bovine serum albumin, the generation of factors V, XI, and XII was clearly demonstrable. On average, after 5 h of perfusion of a single liver, the concentrations in the perfusate (as a percentage of normal rat plasma) were about 6% for factor V, 8% for factor XI, and 5% for factor XII, compared with 20% for factor VII, which was used as the reference standard. When two livers were perfused, approximately twice these concentrations were achieved. When the properties of these factors in perfusate and plasma were compared, they agreed well except for differences in the celite adsorbability of factors XI and XII.