Influence of mithramycin on some platelet functions in vitro

Platelet-rich plasma was incubated with mithramycin in vitro. This diminished platelet aggregation by ADP and adrenaline, but did not interfere with collagen-induced aggregation. Platelet factor 4 release was diminished by ADP and delayed when induced by adrenaline but normal when induced by collagen. Platelet factor 3 availability was not significantly impaired. Reptilase clot retraction was diminished when induced by ADP but normal when induced by collagen. Uptake of 14C-serotonin and 14C-adenine was slightly inhibited. There was no depression in platelet adhesion or release of serum aggregating activity.     

Effect of lomustin on some platelet functions in vitro

The effect of lomustin on platelet functions was investigated in vitro using a wide battery of tests. Lomustin was found to act as a specific inhibitor of platelet aggregation, release reaction and clot retraction and to induce acquired thrombocytopathy. Thus, impairment of platelet functions might play a role in hemorrhagic complications accompanying lomustin therapy in some cases.     

Influence of cis-platinum on some platelet functions in vitro

Cis-platinum added to citrated platelet rich plasma in vitro did not influence the aggregation of the platelets, their adhesion to glass, their release of platelet factor 4 or availability of platelet factor 3 and acid phosphatase. Neither any effect on the uptake of 14C-serotonin, the reptilase clot retraction or the coagulation system has been observed.     

Influence of dianhydrogalactitol on some platelet functions in vitro

Platelet-rich plasma was incubated with dianhydrogalactitol (DAG) in vitro. This moderately diminished platelet aggregation induced by adrenaline and to a smaller degree by adenosine diphosphate /ADP) or collagen. The availability of platelet factor 3 induced by ADP, adrenaline or collagen was decreased irrespective of the inducer. The release of platelet factor 4 was unaffected. Reptilase clot retraction induced by ADP or collagen was slightly inhibited. Uptake of 14C-serotonin was slightly decreased. Uptake of 14C-adenine was normal. Platelet adhesion onto glass was not depressed. DAG did not release lactic dehydrogenase from the cytoplasm of the platelets. Coagulation factors were not affected.     

Intrinsically impaired platelet production in some patients with persistent or chronic immune thrombocytopenia

Persistent or chronic immune thrombocytopenias (P/C‐ITP) are acquired blood disorders lasting more than 3 months or 1 year, respectively. The pathogenesis of these disorders is thought to be immunological. We hypothesized that some patients with P/C‐ITP might have an intrinsic megakaryopoiesis defect. We identified a group of P/C‐ITP patients with acquired isolated mild thrombocytopenia (30–100 × 10⁹/l), undetectable anti‐platelet antibodies, negative autoimmune investigations and no need for treatment. We examined in vitro megakaryocyte differentiation and compared these patients' results with those of acute‐ITP patients and healthy controls. No difference in proliferation, ploidy or expression of surface markers was found. In contrast, P/C‐ITP patients had significantly fewer proplatelet‐forming megakaryocytes. This novel observation demonstrated that some patients diagnosed with P/C‐ITP have an intrinsic megakaryopoiesis defect independent of the bone‐marrow environment. Further investigations are needed to dissect mechanisms underlying this impaired proplatelet formation in these patients.     

ELISA procedures for the characterization of platelet specific antibodies. Evaluation of some variables

BACKGROUND. Characterization of antiplatelet antibodies is often difficult. METHODS. Four similar ELISA procedures for the characterization of the glycoprotein specificity of antiplatelet antibodies were compared. RESULTS. The four techniques gave overlapping results when tested on thirty-five patients' sera containing antiplatelet antibodies. With ten sera the four procedures gave slightly dissimilar results. All the discrepancies consisted of incomplete glycoprotein identification with partial loss of complete glycoprotein complex recognition. CONCLUSIONS. The analysis of the main technical variables led to the following conclusions: a) in some case antiplatelet antibodies recognize non-glycoproteic moieties of the platelet membrane (glyco- and phospholipids): the negative results found when investigating glycoprotein targets were the correct ones; b) the solubilization of unsensitized glycoproteins possibly leads to conformational changes able to mask the antigenic sites, while previous sensitization confers more stability to the molecule; c) best results were obtained using anti-mouse IgG as capturing agent for sensitized glycoproteins: it is likely that this antibody let a larger number of binding sites available for the second antibody.     

Inhibitory effect of aqueous extracts of some herbs on human platelet aggregation in vitro

Effect of aqueous extract of several herbs on human platelet aggregation in vitro was investigated. Out of 28 herbs/nutriceuticals investigated, camomile, nettle alfalfa, garlic and onion exhibited most significant anti-platelet activity (>or=45% inhibition). Aqueous extracts of alfalfa, fresh nettle, and camomile inhibited ADP induced-platelet aggregation by 73, 65 and 60%, respectively, compared with control (P < 0.05). Camomile and alfalfa inhibited collagen-induced platelet aggregation by 84 and 65%, respectively, but nettle could not inhibit collagen-induced aggregation. In contrast, nettle was the most potent inhibitor (66%) of whole blood aggregation induced by collagen, followed by alfalfa (52%), and camomile (30%) compared with control (P < 0.05). None of these three herbs however could inhibit arachidonic acid or thrombin induced platelet aggregation. Camomile and alfalfa strongly inhibited thromboxane B2 synthesis induced by ADP or collagen, but nettle had no effect. Alfalfa and nettle increased cGMP levels in platelets by 50 and 35%, respectively, compared with the control (1.85 +/- 0.23 nM) (P < 0.005). All these data indicate that camomile, nettle and alfalfa have potent anti-platelet properties, and their inhibitory actions are mediated via different mechanisms.     

Inhibitory effect of aqueous extracts of some herbs on human platelet aggregation in vitro

Effect of aqueous extract of several herbs on human platelet aggregation in vitro was investigated. Out of 28 herbs/nutriceuticals investigated, camomile, nettle alfalfa, garlic and onion exhibited most significant anti-platelet activity (≥45% inhibition). Aqueous extracts of alfalfa, fresh nettle, and camomile inhibited ADP induced-platelet aggregation by 73, 65 and 60%, respectively, compared with control (P?<?0.05). Camomile and alfalfa inhibited collagen-induced platelet aggregation by 84 and 65%, respectively, but nettle could not inhibit collagen-induced aggregation. In contrast, nettle was the most potent inhibitor (66%) of whole blood aggregation induced by collagen, followed by alfalfa (52%), and camomile (30%) compared with control (P?<?0.05). None of these three herbs however could inhibit arachidonic acid or thrombin induced platelet aggregation. Camomile and alfalfa strongly inhibited thromboxane B₂ synthesis induced by ADP or collagen, but nettle had no effect. Alfalfa and nettle increased cGMP levels in platelets by 50 and 35%, respectively, compared with the control (1.85?±?0.23?nM) (P?<?0.005). All these data indicate that camomile, nettle and alfalfa have potent anti-platelet properties, and their inhibitory actions are mediated via different mechanisms.     

Investigation of how different filters affect some biochemical properties of stored platelet concentrates.

The aim of the present study was to investigate how four different filters, i.e. Imugard IG500 (Terumo, Japan), Miropore (Miramed, Italy), Pall P1-100 (Pall, USA) and Sepacell P1-10A (Asahi, Japan) affect some biochemical properties of platelet concentrates. The work was conducted using 42 pairs of platelet concentrates. After 2 days of storage, one of the preparations was filtered and the other served as an unfiltered control. Immediately after filtration, determination of the platelet count, desarginated activated complement factor 3 (C3a des arg) and the extracellular and total concentrations of platelet factor 4 (PF4) and lactate dehydrogenase (LDH) were carried out on both these platelet concentrates. After an additional storage period of 3 d, extracellular concentrations of PF4 and LDH were determined on both concentrates. A significant decrease of extracellular PF4 concentration was found immediately after filtration when Pall P1-100 and Imugard IG500 were used. During the 3-d storage after filtration, the concentrates filtered with Imugard IG500 and Pall P1-100 demonstrated significantly higher platelet lysis as compared to the unfiltered controls. It is concluded that the present work demonstrates storage instability after filtration with Imugard IG500 and Pall P1-100. Therefore, platelet concentrates filtered with these filters would not appear to be suitable for storage.     

Influence of cytostatics on some platelet functions in vitro. V. Hydroxyurea.

Hydroxyurea added to citrated platelet-rich plasma in vitro did not influence the aggregation of the platelets, their adhesion to glass, their release of aggregating activity, platelet factor 4 or availability of platelet factor 3. Neither did it have any effect on the uptake of 14C-serotonin, the reptilase clot retraction or the coagulation system.     

A global platelet test of thrombosis and thrombolysis detects a prothrombotic state in some patients with non-insulin dependent diabetes and in some patients with stroke

Platelet aggregation and spontaneous thrombolytic activity were assessed in patients with non-insulin dependent diabetes and stroke using a shear-induced and agonist-induced platelet aggregation test. The Thrombotic Status Analyser (TSA), induces platelet-rich thrombus formation solely by shear forces, while whole blood platelet aggregometry measures platelet reactivity to different agonists. These tests were employed in the present study because in earlier studies they both demonstrated that platelet aggregability in healthy volunteers was unchanged with age. On the other hand, it is known that thrombolytic activity decreases with age in males, but not in females. In diabetic patients shear-induced platelet aggregability varied according to the stage of nephropathy but platelet aggregation to collagen was suppressed at all stages. Platelet reaction to shear stress was enhanced in stroke patients with haemorrhagic episodes but not in patients with lacunar infarction. In contrast, platelet reactivity to collagen was suppressed and changes in ADP-induced platelet aggregability were inconsistent. Suppressed thrombolysis was observed only in diabetes with minor renal defect. Fibrinogen was increased in diabetes with stage III and IV nephropathy. Fibrinopeptide A (FPA) and D-dimer were increased in stroke. Thus, the observed increase in fibrinogen, FPA and D-dimer is inconsistent with changes in platelet aggregability. Our present findings suggest that a shear-induced platelet aggregation test is superior to other tests such as agonist-induced platelet aggregation and thrombotic markers such as fibrinogen, FPA and D-dimer in detecting a prothrombotic state. It is concluded that elderly males may have a prothrombotic state not because of platelet hyper-aggregability but because of suppressed thrombolytic activity. On the other hand, a prothrombotic state in patients with non-insulin dependent diabetes and after stroke may be due to changes in age-independent platelet aggregability.     

A global platelet test of thrombosis and thrombolysis detects a prothrombotic state in some patients with non-insulin dependent diabetes and in some patients with stroke

Platelet aggregation and spontaneous thrombolytic activity were assessed in patients with non-insulin dependent diabetes and stroke using a shear-induced and agonist-induced platelet aggregation test. The Thrombotic Status Analyser (TSA), induces platelet-rich thrombus formation solely by shear forces, while whole blood platelet aggregometry measures platelet reactivity to different agonists. These tests were employed in the present study because in earlier studies they both demonstrated that platelet aggregability in healthy volunteers was unchanged with age. On the other hand, it is known that thrombolytic activity decreases with age in males, but not in females. In diabetic patients shear-induced platelet aggregability varied according to the stage of nephropathy but platelet aggregation to collagen was suppressed at all stages. Platelet reaction to shear stress was enhanced in stroke patients with haemorrhagic episodes but not in patients with lacunar infarction. In contrast, platelet reactivity to collagen was suppressed and changes in ADP-induced platelet aggregability were inconsistent. Suppressed thrombolysis was observed only in diabetes with minor renal defect. Fibrinogen was increased in diabetes with stage III and IV nephropathy. Fibrinopeptide A (FPA) and D-dimer were increased in stroke. Thus, the observed increase in fibrinogen, FPA and D-dimer is inconsistent with changes in platelet aggregability. Our present findings suggest that a shear-induced platelet aggregation test is superior to other tests such as agonist-induced platelet aggregation and thrombotic markers such as fibrinogen, FPA and D-dimer in detecting a prothrombotic state. It is concluded that elderly males may have a prothrombotic state not because of platelet hyper-aggregability but because of suppressed thrombolytic activity. On the other hand, a prothrombotic state in patients with non-insulin dependent diabetes and after stroke may be due to changes in age-independent platelet aggregability.     

血小板输注中抗体检测和配合试验的应用

目的：提高血小板制剂对血小板减少、尤其是血小板输注无效症（PTR）患者的输注疗效,避免宝贵血源的浪费。方法：应用单抗固相微孔板（MASPAT）法检测患者血清中的血小板抗体,进行血小板供者与患者之间的配合试验。结果：2005年6月-2007年11月对109例患者进行了血小板抗体的检测,其中42例患者检出血小板抗体（阳性率38．5％）,对含有血小板抗体的患者经适合性血小板输注后,血小板计数有明显上升。结论：MASPAT法在特异性、敏感性、重复性方面良好,操作快速、简便,判断可靠;易做到规范化,程序化,标准化;据此建立的“适合性血小板输注”对含有血小板抗体的患者是有效的,可用于临床血小板抗体的检测和配合试验。     

Mean platelet volume and mean platelet volume/platelet count ratio in infective endocarditis

Abstract

Infective endocarditis (IE), an infection of the endocardial surface, frequently leads to life-threatening complications, such as thromboembolism due to platelet activation. We investigated the mean platelet volume (MPV) in Korean patients with IE and the serial changes thereof, in comparison with other laboratory parameters. We analyzed 248?MPV results from 22 patients diagnosed with IE in our hospital between January 2011 and April 2012. MPV was measured with an Advia 2120 (Siemens Healthcare Diagnostics, Tarrytown, NY) using EDTA-containing tubes. The mean MPV differed significantly between the patient and control groups, 8.74 vs. 7.96?fl, respectively. In addition, the platelet count and MPV/platelet count ratio were significantly decreased in the patient group. The total platelet mass and platelet size in IE might be increased. Further studies should examine more patients to verify the changes in the MPV and MPV/platelet count ratio in IE and assess in greater detail the relationship between MPV and thrombotic complications caused by platelet activation.     

Phosphorylation of platelet actin-binding protein during platelet activation

In this study we have followed the 32P-labeling of actin-binding protein as a function of platelet activation. Utilizing polyacrylamide- sodium dodecyl sulfate gel electrophoresis to resolve total platelet protein samples, we found 2--3-fold labeling increases in actin-binding protein 30--60 sec after thrombin stimulation. Somewhat larger increases were observed for 40,000 and 20,000 apparent molecular weight peptides. The actin-binding protein was identified on the gels by coelectrophoresis with purified actin-binding protein, its presence in cytoskeletal cores prepared by detergent extraction of activated 32P- labeled platelets, and by direct immunoprecipitation with antibodies against guinea pig vas deferens filamin (actin-binding protein). In addition, these cytoskeletal cores indicated that the 32P-labeled actin- binding protein was closely associated with the activated platelet's cytoskeleton. Following the 32P-labeling of actin-binding protein over an 8-min time course revealed that in aggregating platelet samples rapid dephosphorylation to almost initial levels occurred between 3 and 5 min. A similar curve was obtained for the 20,000 apparent molecular weight peptide. However, rapid dephosphorylation was not observed if platelet aggregation was prevented by chelating external calcium or by using thrombasthenic platelets lacking the aggregation response. Thus, cell-cell contact would seem to be crucial in initiating the rapid dephosphorylation response.