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PubMed2001

Molecular mechanisms involved in human platelet aggregation by synergistic interaction of platelet-activating factor and 5-hydroxytryptamine.

Our recent studies have shown that co-activation of Gq and Gi proteins by 5-hydroxytryptamine (5-HT) and adrenaline show synergism in human platelet aggregation. This study was conducted to examine the mechanism(s) of synergistic interaction of 5-HT and platelet activating factor (PAF) in human platelets. We show that PAF, but not 5-HT, increased platelet aggregation in a concentration-dependent manner. However, low concentrations of 5-HT (2 microM) potentiated platelet aggregation induced by subthreshold concentration of PAF (40 nM) indicating a synergistic interaction between the two agonists and this synergism was blocked by receptor antagonists to either 5-HT or PAF. 5-HT also potentiated the effect of PAF on thromboxane A2 (TXA2) formation and phosphorylation of extracellularly regulated mitogen-activated protein kinases (ERK1/2). The synergism of 5-HT and PAF in platelet aggregation was inhibited by calcium (Ca2+) channel blockers, verapamil and diltiazem, phospholipase C (PLC) inhibitor, U73122, cyclooxygenase (COX) inhibitor, indomethacin, and MEK inhibitor, PD98059. These data suggest that synergistic effect of 5-HT and PAF on human platelet aggregation involves activation of PLC/Ca2+, COX and MAP kinase pathways.

Diltiazem↗
PubMed1990

Translocation-independent activation of protein kinase C by platelet-activating factor, thrombin and prostacyclin. Lack of correlation with polyphosphoinositide hydrolysis in rabbit platelets.

The relationship between polyphosphoinositide hydrolysis and protein kinase C (PKC) activation was explored in rabbit platelets treated with the agonists platelet-activating factor (PAF), thrombin and 12-O-tetradecanoylphorbol 13-acetate (TPA), and with the anti-aggregant prostacyclin (PGI2). Measurement of the hydrolysis of radiolabelled inositol-containing phospholipids relied upon the separation of the products [3H]inositol mono-, bis- and tris-phosphates by Dowex-1 chromatography. PKC activity, measured in platelet cytosolic and Nonidet-P40-solubilized particulate extracts that were fractionated by MonoQ chromatography, was based upon the ability of the enzyme to phosphorylate either histone H1 in the presence of the activators Ca2+, diacylglycerol and phosphatidylserine, or protamine in the absence of Ca2+ and lipid. Treatment of platelets for 1 min with PAF (2 nM) or thrombin (2 units/ml) led to the rapid hydrolysis of inositol-containing phospholipids, a 2-3-fold stimulation of both cytosolic and particulate-derived PKC activity, and platelet aggregation. Exposure to TPA (200 nM) for 5 min did not stimulate formation of phosphoinositides, but translocated more than 95% of cytosolic PKC into the particulate fraction, and induced a slower rate of aggregation. PGI2 (1 microgram/ml) did not enhance phosphoinositide production, and at higher concentrations (50 micrograms/ml) it antagonized the ability of PAF, but not that of thrombin, to induce inositol phospholipid turnover, even though platelet aggregation in response to both agonists was blocked by PGI2. On the other hand, PGI2 alone also appeared to activate (by 3-5-fold) cytosolic and particulate PKC by a translocation-independent mechanism. The activation of PKC by PGI2 was probably mediated via cyclic AMP (cAMP), as this effect was mimicked by the cAMP analogue 8-chlorophenylthio-cAMP. It is concluded that this novel mechanism of PKC regulation by platelet agonists may operate independently of polyphosphoinositide turnover, and that activation of cAMP-dependent protein kinase represents another route leading to PKC activation.

Animals↗
PubMed1994

Flow cytometric detection of circulating activated platelets and platelet hyper-responsiveness in pre-eclampsia and pregnancy.

1. Platelet activation status and response to stimulation with agonists ex vivo were studied by whole blood flow cytometry in 15 women with pre-eclampsia, 20 age- and gestational-age-matched women who completed a normal pregnancy, and 20 age-matched non-pregnant women. 2. Women with proteinuric pre-eclampsia showed evidence of activated, degranulated platelets in the circulation, with increased platelet-bound fibrinogen, increased expression of the lysosomal granule membrane antigen, CD63, and raised plasma levels of beta-thromboglobulin. 3. CD63 expression and beta-thromboglobulin per platelet were also significantly higher in normal pregnant women than in non-pregnant women, but in these subjects fibrinogen binding was normal. 4. There was good correlation for all subjects in degranulation, measured by CD63 antigen expression, and by plasma beta-thromboglobulin levels corrected for platelet count (r = 0.65; P < 0.01). 5. Platelet responsiveness to ADP in vitro showed a heightened degranulation response (CD63 expression) in normal pregnancy compared with the non-pregnant control group, which was increased further in women with non-proteinuric and proteinuric pre-eclampsia. 6. However, this response was not accompanied by an increased binding of fibrinogen to GPIIb-IIIa. Fibrinogen binding in response to 'weak' agonist stimulation, by low concentrations of ADP or, in a subgroup by adrenaline, was in fact lower in the normal pregnant women than in the non-pregnant women. 7. It is postulated that women at risk of developing pre-eclampsia may have hyper-reactive platelets, primed to undergo release by passage through the abnormal placenta.

Adenosine Diphosphate↗
PubMed2001

Platelet activation via the collagen receptor GPVI is not altered in platelets from chronic myeloid leukaemia patients despite the presence of the constitutively phosphorylated adapter protein CrkL.

In this study, we show that the adapter proteins CrkL and Cbl undergo increases in tyrosine phosphorylation and form an intracellular complex in platelets stimulated with the snake venom toxin convulxin, a selective agonist at the collagen receptor glycoprotein VI (GPVI). Constitutive tyrosine phosphorylation of CrkL has previously been reported in platelets from chronic myeloid leukaemia (CML) patients. This was confirmed in the present study, and shown to result in a weak constitutive association of CrkL with Cbl and a number of other unidentified tyrosine-phosphorylated proteins. There was no further increase in phosphorylation of CrkL in CML platelets in response to GPVI activation, whereas phosphorylation of Cbl and its association with CrkL were potentiated. In addition, this was accompanied by a small increase in p42/ 44 mapkinase (MAPK) activity in CML platelets. The functional consequence of the presence of constitutively phosphorylated proteins in CML platelets was investigated by measurement of aminophospholipid exposure and alpha-granule secretion. This revealed little alteration in the concentration-response curves for either in CML platelets stimulated via GPVI, although maximal levels of P-selectin were depressed. Despite the minimal effect on platelet activation in CML patients, we cannot exclude a role for CrkL or Cbl in signal transduction pathways stimulated via GPVI.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Increased platelet Fc receptor expression as a potential contributing cause of platelet hypersensitivity to collagen in diabetes mellitus.

Recent clinical and laboratory observations support a potential role for the platelet FcgammaRIIA receptor (FcR) in collagen-mediated platelet activation associated with arterial thrombosis. Stable age- and sex-independent variation in receptor expression exists. Flow cytometry showed that 100 diabetes patients had increased mean platelet FcR expression levels compared with 201 non-diabetes patients (P < 0.001). Aggregation studies following FcR cross-linking supported a receptor role in increased activation of diabetes platelets after collagen stimulation (P = 0.018). Immunoprecipitation of collagen-stimulated and FcR-crosslinked platelets demonstrated enhanced levels of tyrosine-phosphorylated Syk in diabetic platelets. Increased platelet FcR-mediated sensitivity to collagen may contribute to cardiovascular morbidity and mortality in diabetes.

Adult↗
PubMed2003

The influence of platelet additive solutions on cytokine levels and complement activation in platelet concentrates during storage.

BACKGROUND AND OBJECTIVES: The accumulation of platelet-derived cytokines in platelet concentrates (PC) during storage may contribute towards non-haemolytic transfusion reactions (NHTR). We investigated the effect of platelet storage medium on platelet activation, complement activation and cytokine levels in leucocyte-reduced PC. MATERIALS AND METHODS: Hyperconcentrated platelets (3000-6000 x 109/l) were collected by apheresis and diluted in 100% plasma, 70% PASIII, or 70% or 80% PASIII supplemented with magnesium and potassium (PAS IIIM). RESULTS: Levels of transforming growth factor-beta (TGF-beta) and regulated on activation, normal, T-cell expressed, and secreted (RANTES) increased during storage, as did the expression of P-selectin (CD62P), and were highest in PC stored in PASIII. In PC stored in PASIIIM, however, levels of TGF-beta and RANTES were not significantly different from PC stored in plasma. Levels of CD62P expression, however, remained higher in PASIIIM PC than in those stored in plasma by day 5, but were lower than PC stored in PASIII. C3a des arg levels increased during storage in all media with the exception of PASIII and, on day 7, were higher in PC stored in plasma compared to PC stored in the other media. CONCLUSIONS: Our results indicate that replacing plasma in PC with unmodified PASIII for storage results in higher levels of platelet-derived cytokines in PC. Furthermore, it appears that the nature of the medium used for storage of PC has a significant impact on platelet activation and cytokine levels of the PC. These implications should be taken into account when considering replacement of plasma with PAS.

Blood Platelets↗
PubMed1992

Effects of prestorage white cell-reduction of apheresis platelets on platelet glycoprotein Ib and von Willebrand factor.

Twenty plateletpheresis components were harvested from 11 healthy donors and stored in polyolefin bags on a horizontal flatbed agitator at 22 degrees C. After 24 hours, white cells were reduced in one aliquot by centrifugation while the other aliquot was stored unaltered. Samples were obtained aseptically from each of these platelets at intervals for up to 10 days, and measurements were made of platelet glycoprotein Ib (GPIb) by both flow cytometry and polyacrylamide gel electrophoresis, of ristocetin-induced platelet aggregation by impedance aggregometry, and of plasma and platelet von Willebrand factor (vWF) by enzyme-linked immunosorbent assay. Storage of platelets under these conditions was associated with only minor decreases in surface GPIb, intraplatelet vWF, and ristocetin-induced platelet aggregation, and no differences were observed between the white cell-reduced and nonreduced aliquots. No benefit of white cell reduction in such components before prolonged storage is evident in the vWF-platelet interaction.

Blood Component Removal↗
PubMed1996

Buffy coat platelets stored in apyrase, aprotinin, and ascorbic acid in a suspended bag: combined strategies for reducing platelet activation during storage.

BACKGROUND: Platelet activation is an important factor impeding the clinical effectiveness of platelet transfusions. In this study, platelet concentrates (PCs) were prepared by a novel suspended-bag buffy coat technique that was followed by the addition of a mixture of platelet activation inhibitors to the storage bag. STUDY DESIGN AND METHODS: In vitro platelet function was evaluated in PCs prepared by the suspended-bag buffy coat technique and stored at 22 degrees C for 5 days in the presence of (n = 12) or absence (n = 12) of apyrase, ascorbic acid, and aprotinin (AAA). RESULTS: Platelets from AAA-incubated PCs demonstrated mean ATP levels 17 percent (p < 0.004), 13 percent (p < 0.02), and 22 percent (p < 0.003) higher than those measured in parallel control PCs on Days 1, 3, and 5, respectively. Similarly, on Days 3 and 5 of storage, respectively, 45-percent (p < 0.001) and 50-percent (p < 0.001) greater ADP-induced maximum aggregation was observed in AAA-incubated PCs than was seen in control preparations. AAA-incubated PCs demonstrated alpha-granule membrane protein-140 expression 92 percent (p < 0.01), 133 percent (p < 0.003), and 104 percent (p < 0.001) below that in control PCs on Days 1, 3, and 5, respectively. At similar intervals, a significant increase in recovery from hypotonic shock also was observed in AAA-incubated PCs. Further, Day 5 AAA-PCs demonstrated significantly higher morphology scores and O2 consumption than did control preparations. CONCLUSION: Buffy coat platelets prepared in suspended bags and stored in the presence of AAA demonstrate significantly reduced activation and enhanced functional and metabolic activity.

Aprotinin↗
PubMed1997

Psoralen-mediated photodecontamination of platelet concentrates: inactivation of cell-free and cell-associated forms of human immunodeficiency virus and assessment of platelet function in vivo.

BACKGROUND: Treatment of platelet concentrates (PCs) with psoralens and broad-band ultraviolet A (UVA) radiation is being examined for the elimination of pathogens that might be present in donated blood. Previous studies have demonstrated the inactivation of cell-free viruses and the maintenance of platelet integrity with common in vitro assays. STUDY DESIGN AND METHODS: Human immunodeficiency virus (HIV) in three forms-cell-free, activity replicating, and latently infected cell lines-was added to PCs and treated with 50-microgram per mL of 4'-aminomethyl-4,5',8-trimethylpsoralen (AMT), 0.35 mM rutin, and broad- and narrow-band UVA light (320-400 nm and 360-370 nm [UVA1], respectively). The inactivation of added HIV was assessed in tissue culture; platelet hemostatic activity was assessed in thrombocytopenic rabbits. RESULTS: Each form of HIV was inactivated completely (> or = 10(5) infectious units) on treatment with 30 J per cm2 of UVA1 light. Similar results were obtained on treatment of 2.5 mL of PCs in test tubes or intact PC units (50 mL) in blood bags. Latently infected cell lines were substantially more sensitive than cell-free HIV or HIV that was actively replicating. Human platelets treated with 40 J per cm2 of UVA1 light had a fully corrected bleeding time shortly after treatment or after 5 days' storage, as assessed in thrombocytopenic rabbits. Platelet hemostatic function began to decrease with 81 J per cm2 of UVA1 light and was abolished with 113 J per cm2. At similar fluences, broad-band UVA light was more injurious to platelets than was UVA1 light. CONCLUSION: HIV transmission might be eliminated by PCs after treatment with AMT and UVA1 light and without a reduction in platelet hemostatic function.

Animals↗
PubMedDate not supplied

In vitro inhibitory effect of SR 27417, a potent platelet-activating factor (PAF) receptor antagonist, on the PAF-induced bovine platelet aggregation.

The in vitro inhibitory effect of SR 27417, an antagonist of the platelet-activating factor (PAF) receptor, on PAF-induced platelet aggregation was studied in blood collected from seven healthy Friesien calves. Inhibitory effects of SR 27417 were determined at thirteen different concentrations (0.1-400 nM) by using the dose-response curves of PAF on calf platelet aggregation. In the presence of SR 27417, the maximal slopes of aggregation (%/min) induced by low and high concentrations of PAF were significantly different from the control values obtained without an antagonist at p < or = 0.05 and p < or = 0.01 respectively. In vitro PAF-induced calf platelet aggregation was dose-dependently inhibited by SR 27417. The drug inhibited PAF-induced platelet aggregation in a competitive reversible manner (pA2 = 10.46 +/- 2.36 mol x L(-1)). In conclusion, the results of our study showed that addition of SR 27417 to bovine platelet in vitro inhibits PAF-induced platelet aggregation.

Animals↗
PubMed1995

Phosphoinositide 3-kinase inhibition spares actin assembly in activating platelets but reverses platelet aggregation.

Platelet stimulation by thrombin leads to the activation of phosphoinositide 3-kinase (PI 3K) and to the production of the D3 phosphoinositides, phosphatidylinositol 3,4-bisphosphate (PdtIns-3,4P2) and 3,4,5-trisphosphate (PdtIns-3,4,5-P3). Because changes in the levels of these phosphoinositides correlate with the kinetics of actin assembly, they have been proposed to mediate actin assembly, causing cell shape changes. Wortmannin and LY294002, two unrelated inhibitors of PI 3-K, were used to investigate the role of PI 3-K in platelet actin assembly and aggregation. Both PI 3-K inhibitors abrogated the production of PdtIns-3,4-P2 and PdtIns-3,4,5-P3 in thrombin receptor-activating peptide (TRAP)-stimulated cells. However, neither wortmannin nor LY294002 altered the kinetics of actin assembly or the exposure of nucleation sites in TRAP-stimulated cells. In contrast, PI 3-K inhibitors showed a specific inhibitory pattern of cell aggregation, characterized by a primary phase of aggregation followed by progressive disaggregation. Flow cytometry analysis with the PAC1 monoclonal antibody or with FITC-labeled fibrinogen indicated that wortmannin inhibited the maintenance of the platelet integrin GPIIb-IIIa in its active state. Wortmannin also inhibited, in a dose-dependent manner, platelet aggregation induced by the binding of the monoclonal antibodies P256 and LIBS-6 to GPIIb-IIIa. LIBS Fab-induced aggregation also led to the production of PdtIns-3,4-P2. Platelet secretion, as evidenced by the release of preloaded 14C-5-hydroxy-tryptamine secretion or P-selectin up-regulation, was not affected by PI 3-K inhibition. These results demonstrate that the generation of D3 phosphoinositides is not required for actin assembly in TRAP-activated platelets. However, PI 3-K stimulation is necessary for prolonged GPIIb-IIIa activation and irreversible platelet aggregation. PI 3-K stimulation downstream of GPIIb-IIIa engagement may provide positive feedback required to sustain active GPIIb-IIIa.

Actins↗
PubMed1995

Dystrophin-related protein in the platelet membrane skeleton. Integrin-induced change in detergent-insolubility and cleavage by calpain in aggregating platelets.

The platelet membrane is lined with a membrane skeleton that associates with transmembrane adhesion receptors and is thought to play a role in regulating the stability of the membrane, distribution and function of adhesive receptors, and adhesive receptor-induced transmembrane signaling. When platelets are lysed with Triton X-100, cytoplasmic actin filaments can be sedimented by centrifugation at low g-forces (15,600 x g) but the membrane skeleton requires 100,000 x g. The present study shows that DRP (dystrophin-related protein) sediments from lysed platelets along with membrane skeleton proteins. Sedimentation results from association with the membrane skeleton because DRP was released into the detergent-soluble fraction when actin filaments were depolymerized. Interaction of fibrinogen with the integrin alpha IIb beta 3 induces platelet aggregation, transmembrane signaling, and the formation of integrin-rich cytoskeletal complexes that can be sedimented from detergent lysates at low g-forces. Like other membrane skeleton proteins, DRP redistributed from the high-speed pellet to the integrin-rich low-speed pellet of aggregating platelets. One of the signaling enzymes that is activated following alpha IIb beta 3-ligand interactions in a platelet aggregate is calpain; DRP was cleaved by calpain to generate an approximately 140-kDa fragment that remained associated with the low-speed detergent-insoluble fraction. These studies show that DRP is part of the platelet membrane skeleton and indicate that DRP participates in the cytoskeletal reorganizations resulting from signal transmission between extracellular adhesive ligand and the interior of the cell.

Amino Acid Sequence↗
PubMed1976

Lung responses and platelet release reaction following induced intravascular platelet aggregation in the cat.

Pulmonary microembolism secondary to intravascular platelet aggregation causes a rise in pulmonary vascular resistance and a decrease in dynamic lung compliance. The relationship between these lung responses and the platelet release reaction was investigated in the cat. Repeated episodes of platelet aggregation were induced by intravenous infusions of either ADP or collagen. Platelet release was evaluated by serial determinations of the plasma concentration of platelet factor 4 (PF-4). An increased plasma concentration of PF-4 was found after the initial episode of such induced intravascular platelet aggregation. Consecutive infusions of an aggregating agent still elicited vigorous lung responses, but no further increase in the plasma concentration of PF-4 was observed. There are different possible explanations for this lack of correlation between the lung responses and the PF-4 release. It may well be that the pattern of release for PF-4 does not reflect those release events which result in pulmonary smooth muscle contraction. Alternatively, but less likely, pulmonary smooth muscle constriction and platelet release could be fully independent phenomena.

Adenosine Diphosphate↗
PubMedDate not supplied

Effects of P2Y(1) and P2Y(12) receptor antagonists on ADP-induced shape change of equine platelets: comparison with human platelets.

Platelet activation by adenosine 5' -diphosphate (ADP) is via both P2Y(1 )and P2Y(12) receptors and leads to shape change and aggregation. The effects on ADP-induced platelet shape change of two P2Y(1) antagonists, adenosine 3'-phosphate, 5'-phosphosulfate (A3P5PS) and 2-deoxy-N(6)-methyladenosine 3', 5'-diphosphate (MRS-2179) and a P2Y(12) antagonist 2-propylthio-D-beta,gamma-dichloromethylene-adenosine 5'-triphosphate (AR-C67085MX) were determined by turbidimetric aggregometry and scanning electron microscopy (SEM) on equine and human platelets. The platelet aggregation was inhibited during aggregometry by 4-[4-[4(aminoiminomethyl)phenyl]-1-piperazinyl]-1-piperidin acid hydrochloride trihydrate (GR 144053F), an inhibitor of fibrinogen binding. From aggregation profiles, concentration-response curves and SEM we conclude that the shape change of equine platelets was susceptible to inhibition by the P2Y(1) antagonists A3P5PS and MRS-2179, but less so than human platelets. The P2Y(12) antagonist AR-C67085 did not influence significantly the shape change of either equine or human platelets.

Adenosine Diphosphate↗
PubMed2006

Comparison of changes in circulating platelet-derived microparticles and platelet surface P-selectin expression after coronary stent implantation.

Platelet-derived microparticles (PDMPs) are released from activated platelets and may participate in the inflammatory process in response to vessel wall injury. This study was designed to compare the clinical significance of circulating PDMPs with that of P-selectin on the platelet membrane surface. In 20 patients with stable angina undergoing coronary stent implantation, circulating PDMPs were serially measured by enzyme-linked immunosorbent assay, and P-selectin expression on the surface of platelets was simultaneously analyzed by flow cytometry. PDMPs increased 24-48 h after coronary stenting in the coronary sinus (8.7 +/- 8.9 to 31.8 +/- 19.8 U/ml, P < 0.001) with a maximum at 48 h. In contrast, the mean channel fluorescence intensity for P-selectin increased 15 min after coronary stenting in the coronary sinus (19.5 +/- 5.6 to 25.2 +/- 7.5, P < 0.01) and remained elevated for 48 h; the changes were less striking in peripheral blood. The relative increase in PDMPs was not correlated with the increase in P-selectin expression at 15 min or 24 h after coronary stenting, but was correlated at 48 h (R = 0.48, P < 0.05). Both circulating PDMPs and P-selectin expression were enhanced in association with stent-induced platelet activation; however, the time course of changes in these two platelet activation markers was different. Therefore, the clinical relevance of circulating PDMPs may differ from that of P-selectin expression on the platelet membrane surface.

Aged↗
PubMed1990

CD69 is expressed on platelets and mediates platelet activation and aggregation.

CD69, a surface dimer so far considered an early activation antigen restricted to lymphocytes, was found constitutively expressed on human platelets. Biochemical analysis revealed that platelet CD69 appears on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a broad 55-65-kD band, in which three 55-, 60-, and 65-kD components were detectable when nonreduced, and as two 28- and 32-kD bands when reduced, corresponding to the two disulfide-linked chains of the dimer. It therefore closely resembles lymphoid CD69, although the resolution of the three bands under nonreducing conditions is not usually seen in lymphoid cells. Moreover, as CD69 expressed on activated lymphocytes and CD3bright thymocytes, both chains are constitutively phosphorylated. CD69 stimulation by anti-Leu-23 monoclonal antibodies induced platelet aggregation in a dose-dependent fashion. This effect was associated with Ca2+ influx and platelet degranulation, as revealed by adenosine triphosphate release. In addition, CD69 stimulation in platelets induced production of thromboxane B2 and PGE2, suggesting activation of arachidonic acid metabolism by cycloxygenase. As observed for CD69-mediated T cell activation, platelet activation through CD69 requires molecular crosslinking. These results suggest that CD69 may function as an activating molecule on platelets, as on lymphocytes, and point toward a more general role of this surface dimer in signal transduction.

Adenosine Triphosphate↗
PubMed1981

Antibodies against platelet membrane glycoproteins. II. Influence on ADP- and collagen-induced platelet aggregation, crossed immunoelectrophoresis studies and relevance to Glanzmann's thrombasthenia.

In Glanzmann's thrombasthenia glycoproteins IIb and IIIa are missing or strongly reduced and aggregation to ADP, collagen and thrombin is impaired. Antibodies against glycoproteins IIb and IIIa did not entirely induce a thrombasthenia-like state in normal platelets. However, they did strongly inhibit collagen-induced aggregation and inhibited the second wave of aggregation induced by ADP. Crossed immunoelectrophoresis studies using Triton X-100 extracts of whole platelets with these antibodies gave a single immunoprecipitate. This immunoprecipitate was absent when similar studies were carried out with thrombasthenic platelets. Platelet antibodies gave a number of immunoprecipitates with normal platelets and differences were observed with thrombasthenic platelets, the most notable of which was a marked reduction in one of the major immunoprecipitates. These results provide further evidence that glycoproteins IIb and IIIa are involved in the latter stages of platelet aggregation.

Adenosine Diphosphate↗
PubMed1987

A new familial 'giant platelet syndrome' with structural, metabolic and functional abnormalities of platelets due to a primary megakaryocyte defect.

We have investigated platelet morphology, function and biochemistry in a family affected by dominantly inherited congenital thrombocytopenia with giant platelets. A defect of aggregation was defined with evidence of disturbed fatty acid distribution in platelet membrane phospholipids and impaired arachidonic acid mobilization. Release of 5-hydroxytryptamine was normal. Platelet ultrastructure was grossly abnormal and volume analysis revealed small as well as giant forms. Bone marrow megakaryocytes were morphologically abnormal and the distribution of mean nuclear ploidy atypical, suggesting the production of abnormal platelets due to a primary megakaryocyte disorder. The features of this condition are distinct from those previously described in familial thrombocytopenia and constitute a new "giant platelet syndrome". The qualitative and quantitative platelet defects may be secondary to a disturbance of megakaryocyte cytoplasmic fragmentation.

Adult↗

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