The Formation of Fibrin Around Large Platelet Aggregates (PA’s) in Heparinized Platelet Plasma (PRP)

In concavities on the surface of large PA’s (107-108 μm3) which were produced “spontaneously” or upon addition of ADP 10-6 M in a homogenous shear field in a Couette-type aggregometer (40 s-1), we observed the formation of a fibrin network within 5 mins after sampling. This fibrin network, which could be identified with fluorescent antibodies, formed despite anticoagulation with 7.5 II heparin/ml. The formation of this fibrin network was less pronounced and delayed when the heparin concentration was raised to 20 U/mL 50 U/ml completely suppressed the formation of the network. Concomitantly we found masses of degranulated and ballooned platelets around PA’s with fibrin formation. As we suspected secreted’PF 4 (Antiheparinfactor) being responsible for this phenomenon, we analysed the β-thromboglobulin (β-TC)in heparinized PRP, which is secreted along with PF 4.We found the formation of fibrin not so much correlated to the extent of platelet aggregation in the whole sample, but to the release of β-TG. The samples wherein fibrin was formed, were characterized by β-TG levels in plasma that amounted to up 5% of total platelet protein. In our view this explains the fact, that despite heparinization during extracoporeal circulation the local formation of fibrin-consolidated white thrombi and emboli is observed.

Different Effects of Aspirin, Dipyridamole and UD-CG 115 on Platelet Activation in a Model of Vascular Injury: Studies with Extracellular Matrix Covered with Endothelial Cells

10.1055/s-0038-1661678 ◽

1986 ◽

Vol 56 (03) ◽

pp. 333-339 ◽

Cited By ~ 21

Author(s):

A Eldor ◽

I Vlodavsky ◽

Z Fuks ◽

T H Muller ◽

W G Eisert

Keyword(s):

Extracellular Matrix ◽

Endothelial Cells ◽

Platelet Aggregation ◽

Cyclic Amp ◽

Platelet Activation ◽

Platelet Rich Plasma ◽

Thromboxane A2 ◽

Phase Microscopy ◽

Large Platelet ◽

SummaryCultured endothelial cells produce an extracellular matrix (ECM) which activates platelets, similarly to deendothelialized vascular segments. Platelet-rich plasma (PRP) was incubated with endothelial cells cultures seeded in various densities on ECM. The interaction of the platelets with this artifical intima was evaluated by phase microscopy and by thromboxane A2 (TXA2) and prostacyclin (PGI2) measurement. Large platelet aggregates were formed on exposed ECM. Platelets aggregation but not adhesion on the ECM was markedly inhibited by the presence of endothelial cells. Pretreatment of the endothelial cells with 0.1 mM aspirin reduced their PGI2 synthesis and was associated with platelet aggregation on the ECM. 10 μM dipyridamole markedly inhibited platelet activation by ECM when the drug was added to citrated whole blood before PRP preparation. UD-CG 115 which elevates cyclic AMP in cardiac muscle, inhibited platelet aggregation and TXA2 production induced by ECM, in the presence as well as in the absence of endothelial cells, without any effect on endothelial PGI2 production.

Global Thrombosis Test: Occlusion is attributable to shear-induced platelet thrombus formation.

TH Open ◽

10.1055/a-1704-1022 ◽

2021 ◽

Author(s):

Diana Adrienne Gorog ◽

J. Yamamoto

Keyword(s):

Platelet Aggregation ◽

Experimental Approach ◽

Thrombus Formation ◽

Published Data ◽

High Shear ◽

Coagulation Time ◽

P2y12 Inhibitors ◽

Large Platelet ◽

Platelet Thrombus ◽

Herein, we set out a rebuttal to the publication by Claveria and co-workers published in TH Open this month entitled “Global Thrombosis Test: Occlusion by Coagulation or SIPA?” We strongly believe that the conclusions of their paper, suggesting that occlusion (OT) in the Global Thrombosis Test (GTT) is due to coagulation, rather than shear-induced platelet thrombus formation, is incorrect and the evidence and arguments they present are fundamentally flawed, with major errors both in the experimental approach and in the interpretations of the results. The evidence which they demonstrate, shows that occlusion in the GTT is, in fact, caused by high shear induced platelet thrombus formations. We set out herein the evidence for that, based on histology of the thrombus from the GTT in earlier work using electron microscopy showing large platelet aggregates, the very brief timescale of OT in the GTT compared to coagulation time and the sensitivity of the OT in the GTT to the effects of heparin, t-PA and P2Y12 inhibitors. In addition, we revisit the known pathomechanism of high shear-mediated platelet aggregation to underpin our rationale and show that the modifications to the instrument proposed by Claveria and co-authors would render the technique unphysiological. We highlight several methodological concerns and apparent misinterpreted of the data obtained. We present evidence predominantly from the authors’ own data, together with our earlier published data and evidence from the literature, showing that occlusion in the GTT occurs do to shear-induced platelet aggregation.

Free Platelet Count and Size Distribution During C1q Inhibition of Collagen-Induced Platelet Aggregation

10.1055/s-0038-1645955 ◽

1987 ◽

Vol 58 (02) ◽

pp. 682-685 ◽

Cited By ~ 3

Author(s):

Gyorgy Csako ◽

Eva A Suba

Keyword(s):

Platelet Count ◽

Platelet Aggregation ◽

Light Transmission ◽

Platelet Rich Plasma ◽

Inhibitory Effect ◽

Lag Phase ◽

Large Platelet ◽

Median Volume ◽

Platelet Aggregates ◽

The Mean

SummaryElectronic free platelet counting was more sensitive than turbidimetry to detect collagen-induced platelet activation in human platelet-rich plasma. Purified human Clq exhibited a greater inhibitory effect on collagen-induced platelet aggregation in turbidimetry than free platelet counting. Because the change from small to large platelet aggregates is responsible for the continuing increase in light transmission, Clq was likely more capable of blocking the formation of large platelet aggregates than the formation of small aggregates from single platelets. The iattr uf change by cullagcn in light tiansmissiun and fiec platelet count was reduced in the presence of Clq but the timing of the peak response remained the same. Electronic platelet sizing revealed that the volume of single platelets transiently increased during the turbidimetric “lag phase”. The mean, mode and median volume of the remaining free platelets then decreased, suggesting a selective loss of large, functionally more active platelets and/or platelet degranulation. Clq had no effect on the volume increment during the “lag phase”, but reduced the subsequent fall in the volume of free platelets.

Ticlopidine Facilitates the Deaggregation of Human Platelets Aggregated by Thrombin

10.1055/s-0038-1642389 ◽

1994 ◽

Vol 71 (01) ◽

pp. 091-094 ◽

Cited By ~ 15

Author(s):

M Cattaneo ◽

B Akkawat ◽

R L Kinlough-Rathbone ◽

M A Packham ◽

C Cimminiello ◽

...

Keyword(s):

Cardiovascular Disease ◽

Platelet Aggregation ◽

Prostaglandin E1 ◽

Human Platelet ◽

Adenosine Diphosphate ◽

Human Platelets ◽

Before And After ◽

Normal Human ◽

Platelet Aggregates ◽

Induced Aggregation

SummaryNormal human platelets aggregated by thrombin undergo the release reaction and are not readily deaggregated by the combination of inhibitors hirudin, prostaglandin E1 (PGE1) and chymotrypsin. Released adenosine diphosphate (ADP) plays an important role in the stabilization of thrombin-induced human platelet aggregates. Since ticlopidine inhibits the platelet responses to ADP, we studied thrombin-induced aggregation and deaggregation of 14C-serotonin-labeled platelets from 12 patients with cardiovascular disease before and 7 days after the oral administration of ticlopidine, 250 mg b.i.d. Before and after ticlopidine, platelets stimulated with 1 U/ml thrombin aggregated, released about 80–90% 14C-serotinin and did not deaggregate spontaneously within 5 min from stimulation. Before ticlopidine, hirudin (5× the activity of thrombin) and PGE1 (10 μmol/1) plus chymotrypsin (10 U/ml) or plasmin (0.06 U/ml), added at the peak of platelet aggregation, caused slight or no platelet deaggregation. After ticlopidine, the extent of platelet deaggregation caused by the same inhibitors was significantly greater than before ticlopidine. The addition of ADP (10 μmol/1) to platelet suspensions 5 s after thrombin did not prevent the deaggregation of ticlopidine-treated platelets. Thus, ticlopidine facilitates the deaggregation of thrombin-induced human platelet aggregates, most probably because it inhibits the effects of ADP on platelets.

Accumulation of Macromolecular Particles in the Reticuloendothelial System (RES) Mediated by Platelet Aggregation and Disaggregation

10.1055/s-0038-1651386 ◽

1969 ◽

Vol 22 (03) ◽

pp. 496-507 ◽

Cited By ~ 17

Author(s):

W.G van Aken ◽

J Vreeken

Keyword(s):

Platelet Aggregation ◽

Degradation Products ◽

Reticuloendothelial System ◽

Caproic Acid ◽

Carbon Particles ◽

Carbon Clearance ◽

Aggregation And Disaggregation ◽

SummaryCarbon particles cause platelet aggregation in vitro and in vivo. Prior studies established that substances which modify thrombocyte aggregation also influence the rate at which carbon is cleared from the blood.This study was performed in order to elucidate the mechanism by which the carbon-platelet aggregates specifically accumulate in the RES.Activation of fibrinolysis by urokinase or streptokinase reduced the carbon clearance rate, probably due to generated fibrinogen degradation products (FDP). Isolated FDP decreased the carbon clearance and caused disaggregation of platelets and particles in vitro. Inhibition of fibrinolysis by epsilon-amino-caproic acid (EACA), initially accelerated the disappearance of carbon and caused particle accumulation outside the RES, predominantly in the lungs. It is supposed that platelet aggregation and locally activated fibrinolysis act together in the clearance of particles. In the normal situation the RES with its well known low fibrinolytic activity, becomes the receptor of the particles.

Effects of Bupranolol, a New β-Blocker, on Platelet Functions of Rabbit and Human in Vitro

10.1055/s-0038-1648052 ◽

1976 ◽

Vol 36 (02) ◽

pp. 376-387 ◽

Cited By ~ 3

Author(s):

Teruhiko Umetsu ◽

Kazuko Sanai ◽

Tadakatsu Kato

Keyword(s):

Platelet Aggregation ◽

Platelet Adhesion ◽

Human Platelets ◽

Rabbit Platelet ◽

Rabbit Platelets ◽

Β Blocker ◽

Platelet Aggregates ◽

Induced Aggregation ◽

Platelet Functions

SummaryThe effects of bupranolol, a new β-blocker, on platelet functions were investigated in vitro in rabbits and humans as compared with propranolol, a well-known β-blocker. At first, the effect of adrenaline on ADP-induced rabbit platelet aggregation was studied because adrenaline alone induces little or no aggregation of rabbit platelets. Enhancement of ADP-induced rabbit platelet aggregation by adrenaline was confirmed, as previously reported by Sinakos and Caen (1967). In addition the degree of the enhancement was proved to be markedly affected by the concentration of ADP and to increase with decreasing concentration of ADP, although the maximum aggregation (percent) was decreased.Bupranolol and propranolol inhibited the (adrenaline-ADP-)induced aggregation of rabbit platelets, bupranolol being approximately 2.4–3.2 times as effective as propranolol. Bupranolol stimulated the disaggregation of platelet aggregates induced by a combination of adrenaline and ADP, but propranolol did not. Platelet adhesion in rabbit was also inhibited by the β-blockers and bupranolol was more active than propranolol. With human platelets, aggregation induced by adrenaline was inhibited by bupranolol about 2.8–3.3 times as effectively as propranolol.From these findings. We would suggest that bupranolol might be useful for prevention or treatment of thrombosis.

Systemic Effects of ADP-induced Platelet Aggregation and Their Modification by Aspirin and by Pyridinolcarbamate

10.1055/s-0038-1649115 ◽

1973 ◽

Vol 30 (01) ◽

pp. 178-190 ◽

Cited By ~ 6

Author(s):

Itsuro Kobayashi ◽

Paul Didisheim

Keyword(s):

Platelet Aggregation ◽

Venous Pressure ◽

Systemic Effects ◽

Central Venous ◽

Platelet Aggregates ◽

Induced Changes ◽

Second Wave ◽

Carotid Arterial ◽

Arterial Po2

SummaryADP, AMP, or ATP was injected rapidly intravenously in rats. ADP injection resulted in the f olio wing transient changes: a drop in platelet count, a rise in central venous pressure, a fall in carotid arterial PO2, bradycardia, arrhythmia, flutter-fibrillation, and arterial hypotension. AMP and ATP produced some of these same effects; but except for hypotension, their frequency and severity Avere much less than those following ADP.Prior intravenous administration of acetylsalicylic acid or pyridinolcarbamate, two inhibitors of the second wave of ADP-induced platelet aggregation in vitro, significantly reduced the frequency and severity of all the above ADP-induced changes except hypotension. These observations suggest that many of the changes (except hypotension) observed to follow ADP injection are produced by platelet aggregates which lodge transiently in various microcirculatory beds then rapidly disaggregate and recirculate.

A 3.5-Second Phenomenon in Haemostasis

10.1055/s-0038-1649086 ◽

1973 ◽

Vol 30 (02) ◽

pp. 363-370

Author(s):

D Thilo ◽

E Böhm

Keyword(s):

Bleeding Time ◽

Rat Skin ◽

Fibrin Formation ◽

Bleeding Area ◽

Platelet Thrombus ◽

Platelet Aggregates ◽

Primary Platelet ◽

System Mechanism

SummaryExperiments with injury of the abdominal rat skin were carried out to examine the haemostatic system mechanism in vivo after zero to 30 seconds bleeding time. In the bleeding area only a few platelet aggregates could be found with no primary platelet thrombus. After 3.5 second bleeding time the first fibrin strands have been observed at the site of injury. The hypothesis is put forward that there is a very fast reacting haemostatic mechanism which results in the fibrin formation already at 3.5 seconds.

The Clinical Usefulness of the Platelet Aggregation Test for the Diagnosis of Heparin-Induced Thrombocytopenia

10.1055/s-0038-1651610 ◽

1993 ◽

Vol 69 (04) ◽

pp. 344-350 ◽

Cited By ~ 175

Author(s):

B H Chong ◽

J Burgess ◽

F Ismail

Keyword(s):

Platelet Aggregation ◽

Heparin Therapy ◽

Serotonin Release ◽

Point System ◽

Control Groups ◽

Heparin Induced Thrombocytopenia ◽

Heparin Concentration ◽

Release Test ◽

The Mean ◽

Normal Controls

SummaryThe platelet aggregation test is widely used for the diagnosis of heparin-induced thrombocytopenia (HIT), a potentially serious complication of heparin therapy. We have evaluated its sensitivity and specificity in comparison with those of the 14C-serotonin release test. The sensitivity of the platelet aggregation test was found to vary with the heparin concentration and the donor of the platelets used in the test. The optimal heparin concentrations were between 0.1 and 1.0 U/ml. Using these heparin concentrations, the mean sensitivity varied from 39% (with the least reactive platelets) to 81% (with the most reactive platelets). In comparison, the sensitivity of the release test ranged from 65% to 94%. The specificities of the platelet aggregation test were 82%, 90% and 100% for the following control groups: (1) non-thrombocytopenic patients given heparin, (2) patients with thrombocytopenia due to other causes, and (3) normal controls not given heparin, respectively. The corresponding specificities for the release test was 94%, 90% and 100%. The specificities can be further increased to 100% for all controls with the adoption of a two-point system which defines a positive result as one in which platelet aggregation occurs with a low heparin concentration (0.5 U/ml) but not with 100 U heparin/ml. For optimal results, a two-point platelet aggregation test should be performed with heparin concentrations of 0.5 and 100 U/ml and using platelets of more reactive donors.

Platelet Aggregation Induced in Vitro by Therapeutic Ultrasound

10.1055/s-0038-1651879 ◽

1977 ◽

Vol 38 (03) ◽

pp. 0640-0651 ◽

Cited By ~ 29

Author(s):

B. V Chater ◽

A. R Williams

Keyword(s):

Platelet Aggregation ◽

Direct Action ◽

Adenosine Diphosphate ◽

Ultrasonic Cavitation ◽

Related Phenomenon ◽

Release Reaction ◽

Physical Conditions ◽

Platelet Aggregates ◽

Active Substances

SummaryPlatelets were found to aggregate spontaneously when exposed to ultrasound generated by a commercial therapeutic device. At a given frequency, aggregation was found to be a dose-related phenomenon, increasing intensities of ultrasound inducing more extensive and more rapid aggregation. At any single intensity, the extent aggregation was increased as the frequency of the applied ultrasound was decreased (from 3.0 to 0.75 MHz).Ultrasound-induced platelet aggregation was found to be related to overall platelet sensitivity to adenosine diphosphate. More sensitive platelets were found to aggregate spontaneously at lower intensities of sound, and also the maximum extent of aggregation was found to be greater. Examination of ultrasound-induced platelet aggregates by electron microscopy demonstrated that the platelets had undergone the release reaction.The observation that haemoglobin was released from erythrocytes in whole blood irradiated under identical physical conditions suggests that the platelets are being distrupted by ultrasonic cavitation (violent gas/bubble oscillation).It is postulated that overall platelet aggregation is the result of two distinct effects. Firstly, the direct action of ultrasonic cavitation disrupts a small proportion of the platelet population, resulting in the liberation of active substances. These substances produce aggregation, both directly and indirectly by inducing the physiological release reaction in adjacent undamaged platelets.