John Rogers

Defective Ristocetin-Induced Platelet Aggregation in von Willebrand's Disease and its Correction by Factor VIII

The antibiotic ristocetin, in concentrations of 1.0-1.5 mg/ml, aggregated normal platelets in citrated platelet-rich plasma by a mechanism in which the release reaction played only a minor role. Platelet aggregation by ristocetin in a concentration of 1.2 mg/ml was absent or markedly decreased in 10 patients with von Willebrands disease. Lesser degrees of abnormality were obtained with a concentration of 1.5 mg/ml. The magnitude of the defect in ristocetin-induced platelet aggregation correlated well with the degree of abnormality of the bleeding time and the levels of antihemophilic factor (AHF, VIII(AHF)) procoagulant activity. In all patients, the defect in ristocetin-induced platelet aggregation was corrected in vitro by normal plasma. Correction was also obtained with a fraction of normal cryoprecipitate that eluted in the void volume with VIII(AHF) after chromatography on a gel that excludes molecules larger than 5 x 10(6). A similar fraction, devoid of VIII(AHF) activity, obtained from patients with von Willebrands disease had no corrective effect, but fractions obtained from patients with hemophilia were just as effective as those obtained from normal subjects. The correction activity of plasma and partially purified factor VIII was inhibited by a rabbit antibody to human factor VIII but not by a human antibody against VIII(AHF) procoagulant activity. The studies provide further evidence that patients with von Willebrands disease are deficient in a plasma factor that is necessary for normal platelet function. The activity of this factor appears to be associated with factor VIII but is unrelated to VIII(AHF) procoagulant activity.

Isolated deficiency of platelet procoagulant activity

This is a study of a 34 year old woman with a moderate to severe bleeding disorder in whom impaired platelet procoagulant activity (PPA) was found by several methods, including tests of factor 3 availability (PF-3a), prothrombin consumption and contact activation. No deficiencies of platelet adhesion, aggregation, secretion, metabolism or granule-bound substances were detectable. Under adequate platelet coverage, this woman underwent two surgical procedures without difficulty. These findings demonstrate the role of PPA in hemostasis and indicate that a defect in PPA can be an isolated occurrence. The abnormalities in PF-3a found in this patient could be due to the diminished number of factor V binding sites, resulting in impaired factor Xa binding, found in separate studies by Majerus et al.

Fibrinogen and platelets in the primary arrest of bleeding. Studies in two patients with congenital afibrinogenemia.

Abstract Two patients with a congenital absence of fibrinogen and a prolonged bleeding time were studied to determine the role of fibrinogen in the primary arrest of bleeding and for further clarification of the fibrinogen requirement for platelet function. The retention of platelets, sampled directly from venous blood, in glass-bead filters was consistently decreased and was markedly increased by pretreatment of the beads with fibrinogen. Adhesion of platelets to connective tissue, however, was normal. In citrated platelet-rich plasma (PRP), abnormalities in primary platelet aggregation by ADP and epinephrine were optimally corrected by fibrinogen in concentrations of 10 to 20 mg per 100 ml. In contrast to the abnormal findings in citrated PRP, both primary platelet aggregation and the release reaction were normal in heparinized PRP. The studies leave unanswered the question of the fibrinogen requirements for platelet aggregation, but indicate that fibrinogen is required as a cofactor in the interaction ...

Studies of Platelet 5-Hydroxytryptamine (Serotonin) in Storage Pool Disease and Albinism

Platelets in patients with storage pool disease are markedly deficient in a nonmetabolic (storage) pool of ADP that is important in platelet aggregation. They are also deficient in ATP, although to a lesser degree. In seven patients with this disorder, including one with albinism, platelet 5-hydroxytryptamine (5-HT) levels were reduced in proportion to the reduction in ATP (r = 0.94). Their platelets show diminished capacity to absorb [(14)C]5-HT, and the type of defect was similar to that produced in normal platelets by reserpine, a drug known to inhibit the uptake of 5-HT by the platelet dense granules. Storage pool-deficient platelets also converted more [(3)H]5-HT to [(3)H]5-hydroxyindoleacetic acid than did normal platelets, and the platelets in one of two patients studied contained increased amounts of 5-HT metabolites. The above findings, together with those reported previously, support the conclusion that the capacity of the dense granules (which may be either diminished or functionally abnormal) for storing 5-HT is decreased in storage pool disease; as a result, the 5-HT that enters the platelet may be more exposed to monoamine oxidases present on mitochondrial membranes. This diminished storage capacity (for 5-HT) may also explain why preincubating platelet-rich plasma with 5-HT for 45 min without stirring inhibits subsequent platelet aggregation by 5-HT to a greater degree in patients with storage pool disease than in normal subjects. The latter finding is also consistent with the theory that the aggregation of platelets by 5-HT is mediated by the same receptors on the plasma membrane that are involved in its uptake. The diminished release of platelet-bound [(14)C]5-HT by collagen that we found in these patients, as well as findings in previous studies, suggests that the release reaction may also be abnormal in storage pool disease.

Increased Nerve-Growth-Factor β-Chain Cross-Reacting Material in Familial Dysautonomia

To determine whether dysautonomia arises from alteration in nerve-growth factor (NGF), we measured serum levels of NGF subunits in normal and dysautonomic subjects using a biologic assay based on neurite outgrowth from chick ganglions, a binding assay based on displacement of radiolabeled betaNGF from rabbit-ganglion microsomes, and radioimmunoassays of chi, gamma and betaNGF subunits via antiserum to mouse NGF polypeptides. A threefold increase (P less than 0.001) in serum antigen levels of the biologically active subunit (betaNGF) was found for dysautonomic as compared with normal subjects. By all other assays, the groups were alike. The marked discrepancy in betaNGF levels between antigenic and functional (biologic and binding) measurements suggests a qualitative abnormaltiy of betaNGF in dysautonomia. Alternatively, elevation of betaNGF antigen can be regarded as secondary to disease. This alternative seems less likely since we must then suppose that the normalcy of functional assays in spurious.

Correction of the platelet abnormality in von Willebrand's disease by cryoprecipitate.

Abstract In eleven patients with von Willebrands disease, retention of platelets in glass bead filters was decreased; this abnormality was corrected by prior mixing of their heparinized blood with normal cryoprecipitate. The factor which increased platelet retention was also present in cryoprecipitate prepared from the plasma of a patient with hemophilia but was lacking in the cryoprecipitate of patients with von Willebrands disease. In the more severely affected patients the amount of cryoprecipitate required to correct the defect in retention was larger than in the patients with a lesser hemostatic defect. This crude type of biologic assay suggests that the degree of clinical bleeding in von Willebrands disease may be related to the relative deficiency of a plasma factor necessary for the formation of a hemostatic platelet plug.

Platelet factor 4 in platelet disorders--storage location and the requirement of endogenous ADP for its release.

Summary Platelet factor 4 was present in normal amounts in patients whose platelets are deficient in the storage pool of adenine nucleotides and in the electron–dense granules in which these substances are stored. These findings suggest that PF–4 may be stored in other granules. The release of PF–4 by collagen and epinephrine, however, was decreased in these patients and these findings suggest that the storage pool of ADP may, in addition to being released, play a role in the release mechanism. The findings in patients with thrombasthenia indicate that this is not related to the ability of storage pool ADP to aggregate platelets.