STUDIES ON PLATELET FACTOR-3 AVAILABILITY

IgMk paraprotein from gammopathy patient can bind to cardiolipin and interfere with coagulation assay: a case report

Background

The monoclonal gammopathies are a group of plasma-cell proliferative disorders characterized by the secretion of monoclonal immunoglobulin (M protein or paraprotein). Some rare cases have revealed the specific affinity of paraprotein as autoantibody. Here we report a patient with monoclonal gammopathy of undetermined significance (MGUS) accompanied by a remarkable increase of anticardiolipin antibody (aCL) and an extensively decreased coagulation factor activity, however, without any clinical signs of antiphospholipid syndrome (APS) and bleeding.

Results

Our further investigation indicated that IgMκ paraprotein of this patient possessed an antibody activity against phospholipids so as to bind to cardiolipin and interfere with coagulation assay in vitro.

Conclusions

This case might be indicative that an abnormality of coagulation tests, disturbed by IgMκ paraprotein, does not predict a risk of bleeding in this patient.

In vitro function of random donor platelets stored for 7 days in composol platelet additive solution

Background and Aim:

Platelets are routinely isolated from whole blood and stored in plasma for 5 days. This study was done to assess the in vitro function of random donor platelets stored for 7 days in composol platelet additive solution at 22°C.

Materials and Methods:

The study sample included 30 blood donors of both sex in State Blood Bank, C S M Medical University, Lucknow. Random donor platelets were prepared by the platelet-rich plasma method. Whole blood (350 ml) was collected in anticoagulant Citrate Phosphate Dextrose Adenine triple blood bags. Random donor platelets were stored for 7 days at 22°C in platelet incubators and agitators with and without additive solution.

Results:

Platelet swirling was present in all the units at 22°C on day 7 with no evidence of bacterial contamination. Comparison of the mean values of platelet count, platelet factor 3, lactate dehydrogenase, pH, glucose and platelet aggregation showed no significant difference in additive solution while platelet factor 3, glucose and platelet aggregation showed significant difference (P < 0.001) on day 7 without additive solution at 22°C.

Conclusion:

Our study infers that the platelet viability and aggregation were the best maintained within normal levels on day 7 of storage in platelet additive solution at 22°C. Thus, we may conclude that in vitro storage of random donor platelets with an extended shelf life of 7 days using platelet additive solution may be advocated to improve the inventory of platelets.

In vitro function of random donor platelets stored for 7 days in composol platelet additive solution

BACKGROUND AND AIM

Platelets are routinely isolated from whole blood and stored in plasma for 5 days. The present study was done to assess the in vitro function of random donor platelets stored for 7 days in composol platelet additive solution at 22°C.

MATERIALS AND METHODS

The study sample included 30 blood donors of both sex in State Blood Bank, CSM Medical University, Lucknow. Random donor platelets were prepared by platelet rich plasma method. Whole blood (350 ml) was collected in anticoagulant Citrate Phosphate Dextrose Adenine triple blood bags. Random donor platelets were stored for 7 days at 22°C in platelet incubators and agitators, with and without additive solution.

RESULTS

Platelet swirling was present in all the units at 22°C on day 7, with no evidence of bacterial contamination. Comparison of the mean values of platelet count, platelet factor 3, lactate dehydrogenase, pH, glucose and platelet aggregation showed no significant difference in additive solution, whereas platelet factor 3, glucose and platelet aggregation showed significant difference (P < 0.001) on day 7 without additive solution at 22°C.

CONCLUSION

Our study infers that platelet viability and aggregation were best maintained within normal levels on day 7of storage in platelet additive solution at 22°C. Thus, we may conclude that in vitro storage of random donor platelets with an extended shelf life of 7 days using platelet additive solution may be advocated to improve the inventory of platelets.

Hageman factor, platelets and polyphosphates: early history and recent connection

  Platelet activation and blood coagulation are essential for hemostasis and contribute to a variety of other biological processes such as inflammation, complement activation and tissue repair. Factor (F)XII, originally called Hageman factor, plays an important role in the kallikrein-kinin system by activating prekallikrein. In the 1960s, a platelet activity that promoted FXII activation was identified but its biochemical nature remained unknown. Inorganic polyphosphates (poly P) are polymers that consist of many phosphate residues linked by phosphoanhydride bonds. These polymers exist in all living organisms. In bacteria, poly P is important for growth and survival. Recently, poly P has been identified in human platelet dense granules. Studied have shown that upon platelet activation and secretion, poly P activates FXII, indicating that it is most likely the elusive platelet FXII activator. Poly P also regulates coagulation and fibrinolysis. In this review, we focus on early studies of FXII and the identification of platelet FXII activation activity, and discuss recent findings of poly P in FXII activation and coagulation.

A new activated factor X-based clotting method with improved specificity for procoagulant phospholipid

An improved activated factor X-based clotting method was used to investigate activity of procoagulant phospholipid (PPL) in blood samples collected into various anticoagulants and in plasmas with a range of abnormalities. The dilute activated factor X-activated clotting time (XACT) was carried out on a mixture of specimen with phospholipid-free porcine plasma. PPL from the test sample is then rate-limiting, controlling the clotting time so that the XACT is shortened from a maximum of approximately 120 s with citrated platelet-free plasma to approximately 30 s with freeze-thawed platelet-rich plasma. XACT results were only shortened slightly by fresh normal platelet-rich plasma, but were shortened significantly by platelets that had been activated by freeze-thawing. This improved method for PPL was not prolonged by deficiencies of known clotting factors and therapeutic levels of heparin, and it was surprisingly resistant to most lupus anticoagulants. However, it was extremely sensitive to PPL, detecting down to 50 ng/ml synthetic phospholipid added to phospholipid-free plasma. Excellent correlation was achieved between XACT shortening and microparticle count assessed by annexin V-binding and flow cytometry in normal plasma spiked with platelet microparticles. In citrated blood specimens, XACT shortened with time in a temperature-dependent manner. XACT results on blood samples anticoagulated with ethylenediamine tetra-acetate were more stable, and these would be preferable for assessing PPL expression ex vivo. XACT was significantly shorter in whole blood samples than in normal platelet-rich or platelet-poor plasmas, suggesting that PPL was normally expressed more by cells or aggregates larger than platelets or microparticles.

P1,P4-dithio-P2,P3-monochloromethylene diadenosine 5',5'''-P1,P4-tetraphosphate: a novel antiplatelet agent

We have previously demonstrated in a series of searches for antithrombotic agents that diadenosine 5',5"'-P1,P4-tetraphosphate (AppppA) and its analogues are competitive inhibitors of ADP-induced platelet aggregation. Among various analogues, the P2,P3-monochloromethylene analog of AppppA (AppCHClppA) is superior to unmodified AppppA in its antiplatelet and antithrombotic effects. In this communication, we compare the antiplatelet potency of five newly synthesized agents with that of AppCHClppA. The five new agents include four diadenosine polyphosphate analogues [Ap(s)pCHClpp(s)A (p(s) indicates a thiophosphate), dAppCHClppdA, dAp,pCHClpp(s)dA, and AppCHClpCHClppA], and an adenosine tetraphosphate analogue (AppCHClpCHClp). When tested for their inhibitory effects on platelet aggregation by ADP, the most promising agent among them was Ap(s)pCHClpp(s)A. Both molecular and functional integrity of this compound proved to be stable in blood at 37 degrees C for at least 3 h. It also showed an excellent heat stability. This agent inhibits a number of aspects of ADP-induced platelet activation-e.g., release reaction, cytoplasmic calcium mobilization, thromboxane production, fibrinogen binding sites, and platelet factor 3 activity. Moreover, platelet aggregation induced by agonists other than ADP-e.g., arachidonic acid, collagen, and epinephrine-was inhibited partially by Ap(s)pCHClpp(s)A. It is concluded that (i) Ap(s)pCHClpp(s)A is a promising antiplatelet agent; (ii) it is resistant to blood phosphodiesterases and stable to heat treatment; (iii) platelet aggregation induced by collagen, epinephrine, or arachidonic acid is also inhibited in part by this agent; and (iv) specificity of the inhibitory effects is presented by unmodified adenosine moieties of the agent. Resistance to phosphodiesterases raises the possibility of oral administration.

Platelet factor 3 in plasma fractions: its relation to microparticle size and thromboses

Platelet factor 3 (PF3) was assayed by Russell's viper venom (RVV) in three plasma fractions, platelet-rich plasma (PRP), platelet poor plasma (PPP), and 0.1 microns particle-filtered plasma (PFP), in 42 healthy controls, 34 patients with recent cerebrovascular accidents (CVA) and 28 with recent ischemic events from coronary artery disease (CAD). Platelet microparticles (PMP) were assayed in PPP by flow cytometry. Relative to controls, the RVV clotting times were shortened in all three plasma fractions in both patient groups, p < 0.001. PMP were also elevated in both patient groups, p < 0.001. Linear regression analysis showed that the RVV times of PPP are inversely correlated with PMP, p < 0.005, in patient groups but not in controls. There was no correlation of RVV time with PT, APTT or FIB. After converting RVV times to units of PF3 activity, it could be shown that only about 1/4 of the total PF3 activity was contributed by platelets. The major contribution to the PF3 activity in controls was from microparticles < 0.1 microns but in patients was due mainly to microparticles > 0.1 microns. The RVV time was superior to routine coagulation tests in discriminating thrombotic patients from healthy controls.

Comparative studies of drotaverine--acephyllinate (Depogen) and pentoxifylline (Trental)

Pentoxifylline is an orally active agent for the treatment of peripherial and cerebral vascular diseases. Pentoxifylline increases the deformability of red blood cells in vitro, reduces blood viscosity and decreases platelet aggregation and thrombus formation. Depogen has shown antiaggregatory effect both in vitro and in ex vivo. The inhibitory effect of Pentoxifylline was about 3-5 times weaker than that of Depogen. IC50 = 900/micrograms/ml for Depogén and 3600/micrograms/ml for Pentoxifylline on human platelet rich plasma. Depogen has shown ex vivo antiaggregatory effect on anesthetised rabbits, ID50 = 7 mg/kg in case of iv. administration, and ID50 = 300 mg/kg in case of orally administration. Both compound inhibit the release of platelet precoagulation factor, but the effect of Pentoxifylline was slighter.

Effect of red blood cells from patients with sickle cell disease on platelet factor 3 release

Red cells from two SS genotype and two SA genotype patients were sampled. When the samples were deoxygenated and mixed with platelet-rich plasma, they caused the release of platelet factor 3 as recorded in a coagulometer. This phenomenon was not present in control blood samples from normal individuals. Membrane changes in abnormal red cells during hypoxia may be responsible in part for platelet activation and its role in vasoocclusive crisis. Vasoocclusive crisis could be prevented by increasing the red cell membrane fluidity and inhibiting the platelet aggregation with pentoxifylline.

Analogues of diadenosine 5',5'''-P1,P4-tetraphosphate (Ap4A) as potential anti-platelet-aggregation agents

Dense granules of platelets contain a high content of diadenosine 5',5'''-P1,P4-tetraphosphate (Ap4A). We have previously demonstrated an antithrombotic effect of this compound in a live rabbit model. In the present study we find that certain synthetic Ap4A analogues are superior to Ap4A in inhibiting ADP-induced aggregation of human platelets. Analogues having a P--C--P bridge located in the P2,P3 position of Ap4A are the most potent inhibitors. These analogues are also resistant to hydrolytic enzymes. Analogues having the above characteristics exhibit competitive inhibition with ADP in the ADP-induced platelet aggregation reaction. These compounds, such as AppCHFppA, may be useful as antithrombotic agents. The analogues ApSppSpA and ApSpCHFpSpA also showed good inhibitory effects on ADP-induced platelet aggregation. In addition, this action of Ap4A and its analogues provides an example of a dinucleotide inducing an antagonistic effect by occupying an extracellular mononucleotide binding site on platelets. It calls attention to the possibility that Ap4A and its analogues may act in a similar way in whole organisms, triggering effector or inhibitory responses in any one of a variety of cells.

Hemorheologic effects of Meclomen including effect in malignant melanoma

Sodium Meclofenamate, (Meclomen) (M) is a non-steroidal anti-inflammatory drug, which inhibits both cyclooxygenases and lipooxygenases of the arachidonic acid cascade (AA). (M) inhibited adenosine diphosphosphate (ADP) induced platelet aggregation, arachidonic acid (AA) induced platelet aggregation and collagen induced platelet aggregation. (M) inhibited platelet factor 3 availability when measured by Stypven clotting time. Red cells from patients with advanced malignancies and normal red cells stored in blood banks exhibited loss of deformability. (M) enhanced red cell deformability in these blood samples.

Effect of albumin coating on the in vitro blood compatibility of Dacron arterial prostheses

A recirculating in vitro perfusion system was used to assess the effect of albumin precoating on the thrombogenicity of Dacron vascular grafts. A complete analysis of platelet activation was carried out, involving platelet count, release, adhesion and aggregation. Fibrin formation was assessed by measuring fibrinogen levels and fibrinopeptide A production; leucocyte interaction was analysed by measuring total leucocyte count as well as an analysis of cell adhesion to the surface by scanning electron microscopy. The platelet count decreased progressively with perfusion time for Dacron until by 30 min, it had declined to 69% +/- 2% of baseline. The platelet count did not, however, change significantly from baseline when albumin-coated Dacron was tested. Release of platelet factor 4 and beta-thromboglobulin at 180 min for Dacron was 37.8 +/- 29.8 times and 66.9 +/- 18.2 times baseline, respectively, while albumin coating caused significantly less (P less than 0.03) platelet release. Albumin coating diminished coagulation activation and fibrinopeptide A formation. The total leucocyte concentration decreased significantly for Dacron by 180 min, while that for albumin-coated Dacron did not change significantly from baseline levels. Albumin coating produced a film-like covering over the Dacron. For Dacron, there were numerous leucocytes and platelets adherent to the surface, whilst cellular deposition was minimal upon the albumin-coated surface. Thus, albumin coating improved the short-term blood compatibility of Dacron by all of the methods employed in this study.

Type IIB von Willebrand's disease associated with a complex thrombocytopenic thrombocytopathy

A familial bleeding disorder characterized by an association of Type IIB von Willebrand's disease (vWD) with a complex thrombocytopenic thrombocytopathy is described in two patients from the same generation. Findings typical of type IIB vWD included enhanced ristocetin-induced binding of patient von Willebrand factor (vWF) to platelets of patients and normal individuals in association with the absence of larger multimers from plasma. Abnormalities in platelet function included deficient platelet aggregation to ADP, collagen, epinephrine, and arachidonic acid; and defective release of 14C-serotonin, vWF, and platelet factor 4 (PF4) in response to thrombin, collagen, or ADP. Platelet factor 4 and platelet vWF were decreased when measured per mg of total platelet protein. In addition, the binding of normal vWF to patient platelets stimulated with thrombin was decreased. Platelet size was increased with a very heterogeneous distribution width. Electron microscopic evaluation showed giant platelets with dense and alpha bodies present. The platelet count was borderline or slightly decreased in the resting state and declined to frankly thrombocytopenic levels at the time of acute bleeding episodes; this state was associated with the presence of platelet aggregates in blood smears.

Human platelet interactions with surfaces of type I collagen, chondroitin-4-sulphate, and chondroitin-6-sulphate in vitro

In vitro human platelet interactions with surfaces of type I collagen, chondroitin-6-sulphate (CH-6-S), chondroitin-4-sulphate (CH-4-S), a CH-6-S/collagen layer, and a collagen-CH-6-S complex were investigated. Polystyrene and silanized glass served as controls. Platelet counts, platelet factor 4 released, and platelet aggregating ability for the different surfaces were compared with controls. Platelet count and platelet factor 4 release data showed that there were no differences between surfaces of CH-6-S, CH-4-S and the controls. However, significant differences in platelet counts and platelet factor 4 released were found when collagen, the CH-6-S/collagen layer, and the collagen-CH-6-S complex were compared with controls. The pure type I collagen surface had the greatest influence on platelet activation. The collagen-CH-6-S complex had a greater effect that the CH-6-S/collagen layer on platelet activation. It appears that chondroitin-6-sulphate can modify the platelet activity of type I collagen.

The platelet reactivity of vascular graft prostheses: an in vitro model to test the effect of preclotting

An in vitro perfusion system was used to study the platelet reactivity of the following vascular graft materials when tested with human blood: expanded polytetrafluoroethylene (ePTFE), crimped Dacron Bionit (DB) and preclotted Dacron Bionit (DB/PC). These materials were simultaneously compared to silicone rubber (SR) using an identical perfusion circuit with the same donor's blood. All vascular graft materials tested in this in vitro perfusion system caused some degree of platelet activation as shown by a decrease in platelet count, an increase in platelet factor 3 activity, elevation of plasma levels of both platelet factor 4 and beta-thromboglobulin and decreased platelet aggregability. The observed platelet activation was striking for Dacron and especially preclotted Dacron, with ePTFE showing low levels of platelet activation. Platelet activation by Dacron was initially rapid and then levelled off, whereas the platelet activation with preclotted Dacron began more slowly, but reached much greater levels after three hours of in vitro perfusion.

Some pathophysiological aspects of vibration-induced white finger

The level of sympathetic nervous activity was assessed by evaluating cardiovascular responses to a cold test in 63 vibration-exposed workers (50 subjects without vibration white finger (VWF) and 13 subjects at stages 1 and 2 of VWF) and in 41 controls. Blood pressure, heart rate, systolic time intervals and the skin temperature of the third finger of the right hand were monitored throughout the cold test period. Basal urinary excretion of free catecholamines and platelet aggregation indices both in vitro and in vivo were also determined in all subjects. Systolic time intervals such as electromechanical systole index (QS2I) and left ventricular ejection time index (LVETI) were found to be shorter in the vibration-exposed workers with and without VWF than in the controls, both at rest and during cold exposure and recovery (p less than 0.001). A significant inverse relationship between urinary free catecholamines and the duration of LVETI was observed under resting conditions (p less than 0.03). The recovery rate of the basal finger skin temperature after local cooling was slower in vibration workers with VWF than in those without VWF (p less than 0.05) and in the controls (p less than 0.001). Platelet aggregation indices were similar in all groups studied. The results suggest that the level of sympathetic nervous activity is higher in vibration-exposed workers than in controls. In subjects with VWF, sympathetic hyperactivity in combination with local factors such as vibration-induced hyperresponsiveness to cold of the digital vessels may be responsible for finger blanching attacks.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet collection using the IBM 2997 cell separator

Platelets were collected using the dual-channel module on the IBM 2997 Blood Fraction Separator. We carried out 320 procedures to harvest platelets for therapeutic purposes and yielded 5.1 +/- 1.5 X 10(11) platelets (mean +/- SD). Infusion into previously unsensitized recipients with hypomegakaryocytic thrombocytopenia achieved increments at 1 hr of 19 +/- 7.3 X 10(9)/liter/m2 (mean +/- SD) and at 24 hr of 15 +/- 6.3 X 10(9)/liter/m2. The only consistent donor reaction was mild hypocalcaemia, easily corrected by calcium gluconate infusion. Changes in donor packed-cell volume and white cell count were not statistically altered (p greater than 0.05) but donor platelet counts fell from 216 +/- 43.1 X 10(9)/liter to 162.5 +2- 41.7 X 10(9)/liter (mean +/- SD) (p less than 0.01). Additional plateletphereses were carried out in seven normal volunteers, using the same technique, in order that the function of the harvested platelets could be studied. Following radiochromium labelling and reinfusion into the same donors, normal in vivo recoveries were obtained at 10 min (59.4 +/- 3.4%; mean +/- SD) and platelet mean life span was also normal (218 +/- 12 hr; mean +/- SD). Furthermore, in vitro platelet factor III availability and aggregation patterns of the harvested platelets did not differ from control values and their ultrastructural appearance was normal.

Inherited incomplete deficiency of the fourth component of complement (C4) determined by a gene not linked to human histocompatibility leukocyte antigens

We have studied a family in which the proband had systemic lupus erythematosus and selective incomplete deficiency of the fourth component of complement (C4) (2-5% of the normal level). An additional six healthy family members also had low C4 levels (2.4-24.1% of normal) but no evidence of lupus. This form of inherited C4 deficiency differs from that in previously reported families in that inheritance was autosomal dominant (rather than recessive), C4 levels were markedly reduced (but not undetectable), and there was no linkage to HLA, BF, or C4 structural loci, all known to be within the major histocompatibility complex.

Surface-governed molecular regulation of blood coagulation

Among extracellular biological processes the spatial control of blood clotting is a unique phenomenon. Localization in space has very important consequences in both normal and pathological conditions. Under physiological circumstances a clot is formed only in the vicinity of injury, albeit the prerequisites of coagulation are almost completely given in the whole circulation. The local character of blood clotting is secured by the following major conditions: The regulatory signal initiating coagulation-the damaged vascular wall-is itself a surface on which the majority of clotting reactions take place. The first enzyme, factor XII, of the intrinsic coagulation pathway is activated on the collagen fibers exposed in the damaged vascular wall, although the significance of this reaction in respect of the clotting process is ambiguous. On the membrane of platelets adhered to the damaged blood vessel is activated factor XI, too, which is a well-established participant of the intrinsic clotting process. The further consecutive reactions of coagulation are confined to the surface produced by injury, because the enzymes involved contain gamma-carboxyl-glutamyl side chains which are anchored through calcium bridges to the phospholipids of the platelet membrane. The last enzyme of the sequence is thrombin, which is released from the surface. The reactions taking place on the surface form an enzyme cascade, which amplifies the relatively weak triggering signal by several orders of magnitudes. Amplification is ensured not only by the enzyme-substrate relationship of the consecutive reaction partners, but also by spatial confinement, which endows the process with higher efficacy than could be expected on a statistical basis from reactions in solution. It contributes to the efficiency of enzyme cascade that the non-enzymatic regulatory proteins increase the activity of factors IXa and Xa, and thereby the overall process. While the partner of factor IXa, factor VIII, is captured from plasma, factor V, the partner of factor Xa, is derived from the platelets adhered to the damaged surface and orients the binding of factor Xa. The surface localization ensures the protection of the members of clotting system: In the activator complexes found on the surface, the spatial arrangement of clotting factors prevents the inactivation of factors by physiological inhibitors or by proteolytic enzymes and specific antibodies that appear in the circulation in pathological conditions. Platelet factor 4, derived from platelets, binds heparin and thereby markedly decreases the reactivity of antithrombin III, the physiological inhibitor of clotting factors. The above two circumstances are

Chlorpromazine-induced lupus anticoagulant and associated immunologic abnormalities

Chronic administration of chlorpromazine is associated with the development of a lupus-like circulating anticoagulant and a variety of immunological abnormalities. The prevalence of these findings was studied in 123 psychiatric patients. The anticoagulant was present in 11 of 30 patients receiving chlorpromazine (CPZ), in none of 17 patients who had been off phenothiazine therapy for over a year and in none of 53 controls. It was also seen in 5 of 13 patients who had been switched from CPZ to another phenothiazine even after several years being off CPZ. The anticoagulant was characterized by prolongation of the partial thromboplastin time, thromboplastin dilution test, and Russell's viper venom time. Washed frozen platelets partially corrected the abnormality induced by the anticoagulant. In all but one case the anticoagulant was associated with positive antinuclear antibody test and/or increased serum IgM. Six of 16 patients also had decreased complement levels, and two had a positive direct Coombs' test. None of these patients manifested bleeding, hemolysis, splenomegaly, or other clinical features of systemic lupus erythematosus.

Morphological and functional disturbances of platelets induced by cryopreservation

In vitro morphological and functional studies were carried out on platelets which had been cryopreserved in the presence of 5% dimethyl sulphoxide (DMSO). Overall loss of platelets was around 50%. Those which survived freezing and reconstitution showed marked morphological deterioration, increase of procoagulant activity (PF3a) and a decrease in their aggregability and adenine nucleotide content. We conclude that if transfused, cryopreserved platelets are likely to be less effective than fresh platelets and may activate coagulation in vivo and that they should only be used when suitable fresh platelets are not available.

Blood-materials interactions: the minimum interfacial free energy and the optimum polar/apolar ratio hypotheses

Numerous hypotheses exist to explain observed blood-materials interactions. It is the purpose of this article to test two popular hypotheses, namely, the minimum interfacial free energy hypothesis and the optimum polar/apolar ratio hypothesis. Methacrylate polymers and copolymers were characterized using the captive bubble underwater contact angle method; bulk water content was determined by gravimetric methods; streaming potential measurements were made; and surface roughness and possible particulate contamination were evaluated by reflected light microscopy. In vitro blood tests include whole blood clotting time measurements on polymer-coated tubes; centrifugal force platelet adhesion on polymer-coated coverslips; and a measure of the partial thromboplastin time, Russell's viper venom time (Stypven time), and the prothrombin time of native whole blood exposed to polymer-coated microscope slides. Results suggest that platelet adhesion correlates in the opposite direction of whole blood clotting time and partial thromboplastin time, emphasizing the need for a multiparameter approach to blood-materials testing. Based on these tests the minimum interfacial free energy hypothesis is not supported. In fact, the data suggest the opposite to be true. It is apparent that platelet adhesion can be a misleading indicator of blood compatibility. Neither hypothesis can explain the apparent conflict between the platelet adhesion data and the coagulation time data.

Standardization of platelet function tests

Methods for the standardization of several currently used platelet function tests (bleeding time, capillary fragility, platelet retention, platelet aggregation, platelet factor 3, and platelet volume profiles) are presented, Different variables than may interfere with the reproducibility of the results of each assay were identified and standardized. Using the standardized techniques, the range of normal values for each test was determined in a large population of normal volunteers and used to identify disease states by comparing patient results with those of the normal population. A format for presenting the entire profile of platelet function parameters is proposed.

Haemorrhagic thrombocytopathy associated with dilatation of the platelet--membrane complex

We evaluated eight patients from four families because of a history of excessive bleeding. Most patients had prolonged bleeding times, absent secondary wave of platelet aggregation in response to epinephrine, collagen and adenosine diphosphate (ADP), and defective 14C-serotonin release and platelet factor 3 availability. These findings are characteristic of a platelet release defect. Electron-microscopy examination of the platelets of seven patients revealed a common abnormality. From 30% to 70% of the platelets in any given sample exhibited a prominent membrane complex and dilated, tortuous surface-connected canalicular system ('swiss-cheese' platelet). In two patients there was coincident storage-pool disease, but the remainder had adequate dense bodies and a normal ratio of ATP to ADP. SDS-polyacrylamide gel electrophoresis of platelet proteins and glycoproteins showed no abnormalities. The patency of the canalicular system was demonstrated in one patient by the observation that dense bodies appeared in the cannaliculi and outside the platelets following collagen-induced aggregation of polylysine-treated platelets. Since platelet-aggregation responses to the calcium ionophore A23187 were normal, we conclude that the defective platelet function in these patients may be due to impaired calcium mobilization from the morphologically abnormal membrane complex.

Labile anticoagulant in a patient with lymphoma

A patient with diffuse lymphocytic lymphoma and monoclonal IgM kappa immunoglobulin was found to have an unstable circulating anticoagulant. The anticoagulant inhibited phospholipid-dependent plasma coagulation reactions. Unlike previously described anticoagulants of this type, this plasma inhibitor was neutralized in vitro by products of platelet lysis but not by exogenous addition of other phospholipids or by intact platelets. Inhibitory activity seemed dependent on the monoclonal immunoglobulin, but isolated immunoglobulin fractions lacked anticoagulant activity, suggesting that the inhibitory function was dependent on an easily disrupted macromolecular aggregate. Recognition and characterization of other similar anticoagulants may provide a means of studying the role of phospholipids in normal hemostasis.

Quinine- and quinidine-dependent antiplatelet antibodies. Requirement of factor VIII-related antigen for platelet damage and for in vitro transformation of lymphocytes from patients with drug-induced thrombocytopenia

The requirement of Factor VIII-related antigen (VIIIR:Ag) for platelet damage by quinine-and quinidine-dependent antibodies was studied in platelet-rich plasma (PRP) of four patients with severe von Willebrand's disease (vWd) (Factor VIII deficiency). Platelet factor 3 availability, platelet aggregation, and release of [(14)C]serotonin from labeled vWd-PRP by drug-dependent antibodies were significantly reduced in comparison with PRP from normal controls. Addition of purified VIIIR:Ag restored levels of platelet damage to that of normal PRP. In vWd-PRP, platelet damage by two human antiplatelet sera, not dependent on drugs, and by a rabbit antiplatelet serum did not differ from that in normal PRP. PRP from patients deficient in Factor VIII coagulant activity, Factor IX, or Factors II, VII, IX, and X behaved like normal PRP. The role of VIIIR:Ag in forming antigen able to transform lymphocytes of patients who had recovered from drug-induced thrombocytopenia was investigated by measuring incorporation of [methyl-(3)H]thymidine into DNA. When lymphocytes were cultured for 7 d, significantly less transformation occurred in response to platelets and the drug in the presence of vWd sera than in normal sera or sera deficient only in Factor VIII coagulant activity or Factor IX. Addition of purified VIIIR:Ag to vWd sera restored transformation to that obtained in normal sera. Nonspecific lymphocyte transformation by pokeweed mitogen was not affected by VIIIR:Ag. Thus VIIIR:Ag is involved both in platelet damage by drug-dependent antibodies and in the interaction between platelet and drug which produces an antigen able to transform sensitized lymphocytes.

Effect of ionizing radiation on platelet function in vitro

The effect of ionizing radiation on platelet function was investigated in vitro. Platelet-rich plasma (300 x 10(9/1)) was irradiated with doses of 1, 4, 10, 20 and 50 Gy. Platelet function tests were performed on both irradiated and control (non-irradiated) platelet samples. The platelet function tests were (1) platelet aggregation by ADP (1, 2, 4 mumol final concentration), adrenaline and collagen, (2) ADP-release from platelets, (3) clot retraction and (4) platelet factor-3 availability. It was found that roentgen irradiation of platelets in vitro did not affect these platelet functions tests.

Inhibition of platelet factor 3 availability by prostacyclin

Preincubation of human platelet rich plasma with PGI2 in a concentration preventing collagen induced platelet aggregation abolished also platelet factor 3 availability brought about by collagen. Following PGI2 pretreatment no second wave aggregation could be elicited by ristocetin. However, primary aggregation as well as platelet factor 3 activity were only partially inhibited in this case and the inhibitory action of PGI2 was not increased by raising its concentration. Similarly, marked but not complete inhibition of platelet factor 3 availability was obtained when kaolin was used as activating agent.

Monoclonal immunoglobulin M lambda coagulation inhibitor with phospholipid specificity. Mechanism of a lupus anticoagulant

Prolongation of all phospholipid-dependent coagulation tests was found in a patient with macroglobulinemia, despite absence of bleeding manifestations. The purified monoclonal IgM lambda protein and its Fabmu tryptic fragment induced similar changes in normal plasma. Patient IgM and Fabmu completely inhibited Ca++-dependent binding of radiolabeled prothrombin and Factor X to mixed phospholipid micelles. The patient's IgM lambda paraprotein reacted with phosphatidylserine and, to a lesser extent, with phosphatidylinositol and phosphatidic acid, but not with phosphatidylcholine or phosphatidylethanolamine. Prior incubation of phospholipid with patient Fabmu blocked the positive reactions. Substitution of washed platelets for phospholipid led to normalization of patient coagulation tests and corrected all abnormalities produced in normal plasma by patient IgM. Furthermore, binding of 125I-Factor Xa to thrombin-treated platelets was entirely normal in the presence of patient IgM. These studies support the concept that platelets, rather than phospholipid micelles, are the primary locus of prothrombin and Factor X activation in normal hemostasis.

Blood fluidity and coagulation phenomena in chronic arterial occlusive disease

Blood fluidity depends on a number of factors of which especially the deformability of erythrocytes is of importance. Investigations reported in this paper have revealed an interdependence between blood fluidity and coagulability of blood. They confirm the significance of maintaining red cells deformability if an adequate microcirculation is to be provided in patients with occlusive vascular disease. High doses of oral pentoxifylline are able to improve erythrocyte flow rates in patients with occlusive vascular disorder. This agent also decreases platelet hyper-reactivity, a factor of importance in arresting the arteriosclerotic progression. In addition the hypercoagulability existing in such patients is reduced and the fibrinolytic system stimulated by treatment with the drug.

Coagulation studies in rheumatic heart disease

The clotting characteristics of pulmonary and systemic blood were studied in 10 patients with chronic rheumatic mitral valve disease complicated by atrial fibrillation and in seven patients with aortic valve disease in sinus rhythm. A haemostatic basis for the association of rheumatic mitral valve disease with thrombotic emboli was sought. Both groups of patients showed differences in platelet function between pulmonary and systemic arterial blood. In patients with mitral valve disease aggregation of platelets was significantly greater in pulmonary than in systemic arterial blood at rest; the converse was true during exercise. In aortic valve disease platelet aggregation was greater in systemic than in pulmonary arterial blood at all times. Only the patients with mitral valve disease showed changes in blood coagulation during passage through the lungs and left heart; there was a small but statistically significant shortening in partial thromboplastin time in systemic as compared with pulmonary arterial blood both at rest and during exercise. Similarly, the effects of exercise on the various haemostatic factors measured were largely confined to the patients with mitral valve disease; in these patients exercise stimulated an increase in factor VIII in pulmonary arterial blood and an increase in platelet adhesiveness and aggregability in left heart blood. These changes provide a basis for the suggestion that in patients with rheumatic mitral valve disease, unlike those with aortic valve disease, there is an increased thrombotic tendency in blood in the left heart which is particularly pronounced during exercise.

Correlations between age-dependent protein and lipid concentrations in plasma and platelet functions in children

The correlations between the levels of various plasma proteins and lipids and platelet function on glass and platelet factor 3 (PF 3)-availability in children of different age-groups were investigated. Several statistically significant positive and some significant negative correlations were found. Although conclusions based solely on such correlations should be considered with reservation, in our opinion the following factors should stimulate platelet function: prealbumin (adhesion and PF 3-availability in all age-groups, aggregation--specifically for children in puberty); alpha 1-antitrypsin (PF 3-availability); alpha 2-macroglobulin (platelet spreading capacity, PF 3-availability); plasminogen (platelet adhesion and aggregation--specifically for boys in puberty); caeruloplasmin (number of "free adhering platelets" spreading capacity); lysolecithin and lecithin (time-dependent increase of spontaneous platelet adhesion and aggregation, PF 3-availability); and free fatty acids (FFA) (PF 3-availability). Plasminogen and complement component C'3 show a negative relationship to the time-dependent increase of spontaneous platelet adhesiveness and aggregability in platelet-rich plasma.

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.