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In recent years autologous platelet concentrates (APCs) have become popular in several medicine fields, representing a valuable adjunct to regenerative surgical procedures. Beneficial effects in the control of postsurgical discomfort and infection have also been frequently reported, suggesting that APC may possess anti-inflammatory and antimicrobial properties. The aim of the present review was to summarize the current evidence regarding the antimicrobial effects of platelet concentrates, investigated byin vitroand animal studies. This review was conducted following a systematic approach. An electronic search was performed on MEDLINE, EMBASE and Scopus databases using appropriate search terms, without language or time restrictions. Preclinical studies assessing the antimicrobial activity of APC were included and divided according to the experimental design. Twentyin vitrostudies and four animal studies, investigating APC effects on a broad range of microorganisms, were included. Inin vitrostudies APC reduced the growth of microorganisms during the first hours of incubation, while they could not completely break down the microbial load. In fact, over time a recovery of bacterial growth was always observed, suggesting that APCs display a bacteriostatic rather than a microbicidal activity. All animal studies showed that APC administered by local injections were able to reduce the infection caused by different microorganisms, although to a lesser extent compared to antibiotics. In conclusion, although the exact action mechanisms of interaction with microbial pathogens need further investigation, platelet concentrates proved to have antimicrobial properties, and therefore could represent a useful natural substance for controlling postoperative infections at surgical sites. [ABSTRACT FROM AUTHOR]

It has been demonstrated recently in several solid tumors that thrombocytosis at diagnosis may correlate with tumor invasion, metastatic progression and worse outcome. Several details of the pathomechanism of the relationship of thrombocytosis and cancer have been elucidated; however, the complete process is not clearly understood. Several hypotheses have been proposed. Recently, it was suggested that in ovarian cancer elevated IL-6 production by the tumor may induce increased megakaryopoiesis via hepatic thrombopoietin production leading to thrombocytosis. The importance of the prognostic power of elevated platelet count is still debated in gastrointestinal cancer. The aims of this review were to evaluate the prognostic significance of thrombocytosis in gastrointestinal tumors, to see whether clinical practice confirmed the hypotheses and to reveal the causes of the inconsistent findings. [ABSTRACT FROM AUTHOR]

Stromal cell-derived factor-1 (SDF-1), signaling through CXCR4, is implicated in megakaryopoiesis and platelet production. SDF-1 rs2297630 is a functional polymorphism in linkage disequilibrium with other functional variants in SDF-1. This study aimed to investigate the role of SDF-1 rs2297630 in chronic ITP. The genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism and confirmed by direct sequencing. Immature platelet fraction (IPF) was performed using Sysmex XE-2100. Anti-platelet autoantibodies were assayed by enzyme-linked immunosorbent assay. The main characteristics at diagnosis and the outcome of chronic ITP in 201 Chinese patients were retrospectively reviewed. There was no significant difference in either genotype or allelic distribution between ITP patients and the controls (p= 0.114;p= 0.787). However, both heterozygote (GA) and homozygote minor allele (AA) patients had significantly increased megakaryocyte quantity compared to homozygote genotype (GG) patients at diagnosis (p =0.011). The mean IPF values of GA and AA genotype patients were higher than those observed in the GG genotype patients when platelet counts ≤50 × 109/L at diagnosis (p= 0.007). Patients with GA and AA genotype showed a higher response rate to standard treatments than patients with GG genotype (p< 0.001). In particular, GA and AA genotype patients had a significantly increased chance of responding to steroids, intravenous immunoglobulin (IVIG), and thrombopoietin analogs (p= 0.007;p= 0.029;p= 0.034, respectively). No significant difference was found between anti-platelet antibodies and genotypes (p= 0.296). In summary, the SDF-1 rs2297630 was associated with platelet production and treatment response in Chinese patients with chronic ITP. [ABSTRACT FROM AUTHOR]

Background: Imbalance in hemostatic mechanisms can occur during pregnancy with a tendency for hypercoagulability and increased thrombosis risk. Pregnant women with hypertensive disorder, especially preeclampsia, show alterations in platelet indexes. Immature platelet fraction (IPF) has been suggested as a sensitive index for monitoring changes in platelet production and destruction.Objectives: To evaluate the IPF in patients diagnosed with a gestational hypertensive disorder (GHD).Patients and methods: A cross-sectional study was conducted at an University Hospital to estimate maternal blood IPF index in 99 pregnant women, divided into three groups: normotensive pregnancy (NP), preeclampsia syndrome (PES), and non-proteinuric hypertensive pregnancy (nPHP). Following ethical approval and written informed consent, samples were collected from 33 NP, 34 PES, and 32 nPHP women. Platelet indexes were measured by fluorescent flow cytometry.Results: IPF and mean platelet volume (MPV) counts in GHD were significantly higher than in NP (IPF: 3.8, 2.4–5.1%; 8.6, 5.8–10.6%; 7.3, 4.2–10.2%;p< 0.001 and MPV: 10.6 ± 0.9 fL; 12.1 ± 1.0 fL; 11.6 ± 1.0 fL;p< 0.001 for NP, PES, and nPHP, respectively). No difference was detected between PES and nPHP groups. The distribution of patients with an IPF above 6.1%for NP, PES, and nPHP was 9%, 65%, and 43.8%, respectively (p< 0.001). IPF as a test to differentiate GHD from the controls achieved an area under the curve of 0.83 on a receiver operating characteristics curve.Conclusion: A distinct profile in platelet indexes was detected in hypertensive pregnancies. It suggests that these markers could be used in daily routine as an additional tool in the management of pregnant women. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate whether rare missense genetic variants in several genes related to platelet functions and acetylsalicylic acid (ASA) response are associated with the platelet reactivity in patients with diabetes type 2 (T2D) on ASA therapy. Fifty eight exons and corresponding introns of eight selected genes, including PTGS1, PTGS2, TXBAS1, PTGIS, ADRA2A, ADRA2B, TXBA2R, and P2RY1 were re-sequenced in 230 DNA samples from T2D patients by using a pooled PCR amplification and next-generation sequencing by Illumina HiSeq2000. The observed non-synonymous variants were confirmed by individual genotyping of 384 DNA samples comprising of the individuals from the original discovery pools and additional verification cohort of 154 ASA-treated T2DM patients. The association between investigated phenotypes (ASA induced changes in platelets reactivity by PFA-100, VerifyNow and serum thromboxane B2 level [sTxB2]), and accumulation of rare missense variants (genetic burden) in investigated genes was tested using statistical collapsing tests. We identified a total of 35 exonic variants, including 3 common missense variants, 15 rare missense variants, and 17 synonymous variants in 8 investigated genes. The rare missense variants exhibited statistically significant difference in the accumulation pattern between a group of patients with increased and normal platelet reactivity based on PFA-100 assay. Our study suggests that genetic burden of the rare functional variants in eight genes may contribute to differences in the platelet reactivity measured with the PFA-100 assay in the T2DM patients treated with ASA. [ABSTRACT FROM AUTHOR]

Considerable evidence has been accumulated concerning the roles of platelets in immune responses. In the present study, we examined the functional modulation of macrophages by platelets. When mouse bone marrow-derived macrophages (BMDMs) were co-cultured with platelets, BMDMs produced lower levels of nitric oxide (NO), tumor necrosis factor-α (TNF)-α, and interleukin (IL)-6 in response to a bacterial endotoxin (LPS) and zymosan. The attenuation in the macrophage susceptibility to LPS appeared to be mediated by soluble factors secreted from platelets. The mRNA levels of NOS2 (iNOS), TNF-α, and IL-6 in LPS-stimulated BMDMs that had been cultured with a conditioned medium of platelets were also decreased as analyzed by RT-qPCR. The ability of the platelet-conditioned medium to suppress macrophage NO production was recovered in a high-molecular-weight fraction (>670 kDa) after gel-filtration chromatography on a Superose 6 column. These results suggest that platelets control the susceptibility of macrophages to prevent excessive responses to LPS and provide mechanistic insight into a previous report that experimental thrombocytopenia aggravated organ failure in LPS-induced endotoxemia. [ABSTRACT FROM AUTHOR]

Platelets are critical for maintaining vascular hemostasis, but also play a major role in the formation of occlusive cardiovascular and cerebrovascular thrombi under disease conditions. Secretion of platelet alpha and dense granules is a requirement for efficient thrombus formation. Understanding and targeting the mechanisms of secretion is important to aid the development of effective antithrombotics. SNAP29 is a tSNARE found in platelets, but whose role has not been defined. Using a platelet-specific SNAP29 knockout mouse model, we assessed the role of SNAP29 in platelet secretion and function under standardized conditions and also inin vitroandin vivothrombosis. The data showed no major defects in SNAP29-null platelets, but revealed a minor defect in α-granule secretion and a significant increase in embolization rate of thrombiin vivo. These data suggest that SNAP29 contributes to the regulation of platelet α-granule secretion and thrombus stability, possibly partially masked by functional redundancy with other tSNAREs, such as SNAP23. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the distribution of platelet reactivity values in patients treated with prasugrel and ticagrelor. This prospective observational study enrolled 200 patients treated with prasugrel or ticagrelor. Platelet aggregation was determined by multiple electrode aggregometry after stimulation with adenosine diphosphate (ADP) in the maintenance phase of treatment with prasugrel or ticagrelor. Only 3% of patients in the prasugrel group and 2% of study participants in the ticagrelor group had high on treatment platelet reactivity (HTPR). The majority of patients displayed low on treatment platelet reactivity (LTPR; prasugrel: 69%; ticagrelor: 64%). The pharmacodynamic effect was similar in patients treated with prasugrel and ticagrelor: the median level of ADP-induced platelet aggregation was 15U (interquartile range IQR 9-21U) under prasugrel treatment and 17U (IQR 8–24U) under ticagrelor treatment (p=0.370). In conclusion, our study suggests that there is some degree of variability in ADP-induced platelet aggregation under treatment with prasugrel and ticagrelor. [ABSTRACT FROM AUTHOR]

In vitromodels of thrombocytopenia are useful research tools. Previously published models have shortcomings altering properties of platelets and other blood components. The aim of the present study was to develop a whole blood method to induce thrombocytopenia with minimal manipulation, and to describe platelet function in induced thrombocytopenia in individuals with healthy platelets. Hirudin anticoagulated blood was obtained from 20 healthy volunteers. One part of the blood was gently centrifuged at 130gfor 15 minutes. The platelet-rich plasma was replaced with phosphate-buffered saline to establish thrombocytopenia. Various levels of thrombocytopenia were achieved by combining different volumes of baseline whole blood and thrombocytopenic blood. Platelet counts were measured by flow cytometry (Navios, Beckman Coulter) and routine haematological analyser (Sysmex XE-5000). Platelet function was analysed by impedance aggregometry (Multiplate® Analyzer, Roche) and by flow cytometry (Navios, Beckman Coulter) using collagen, adenosine diphosphate, thrombin receptor activating peptide-6 and ristocetin as agonists. Median baseline platelet count was 227×109/l. Thein vitromodel yielded median platelet counts at 51×109/l (range 26–93×109/l). We observed minor, yet significant, changes in platelet size and maturity from baseline to modelled thrombocytopenia. In the thrombocytopenic samples, significant and positive linear associations were found between platelet count and platelet aggregation across all agonists (allp-values<0.001). Platelet function assessed by flow cytometry showed minimal alterations in the thrombocytopenic samples. A new whole blood-based model of thrombocytopenia was established and validated. This new model serves as a useful future tool, particularly to explore platelet function in patients with thrombocytopenia. [ABSTRACT FROM AUTHOR]

Patients with thrombocytopenia or platelet disorders are at risk of severe bleeding. We report the development and validation of flow cytometry assays to diagnose platelet disorders and to assess platelet function independently of platelet count. The assays were developed to measure glycoprotein levels (panel 1) and platelet function (panel 2) in sodium citrated blood. Twenty healthy volunteers and five patients diagnosed with different platelet disorders were included. Glycoprotein expression levels of the receptors Ia, Ib, IIb, IIIa and IX were measured and normalised with forward scatter (FS) as a measurement of platelet size. Platelet function was assessed by CD63, P-selectin and bound fibrinogen in response to arachidonic acid, adenosine diphosphate (ADP), collagen-related peptide, ristocetin and thrombin receptor-activation peptide-6. All patients except one with suspected δ-granule defect showed aberrant levels of glycoproteins in panel 1. Glanzmann's thrombasthenia and genetically verified Bernard–Soulier syndrome could be diagnosed using panel 1. All patients showed reduced platelet function according to at least one agonist. Using panel 2 it was possible to diagnose Bernard–Soulier syndrome, δ-granule defect and GPVI disorder. By combining the two assays, we were able to diagnose different platelet disorders and investigate platelet function independent of platelet count. [ABSTRACT FROM AUTHOR]

Serum thromboxane-B2 (TxB2), together with arachidonic acid (AA)-induced platelet aggregation, are, at the moment, the most used tests to identify patients displaying high on-aspirin treatment platelet reactivity (HAPR). Both tests are specific for aspirin action on cyclooxygenase-1. While the correlation between serum TxB2 assay and clinical outcome is established, data are conflicting with regard to aspirin treatment and a possible association with AA-stimulated platelet markers and clinical outcome. To understand such discrepancy, we performed a retrospective study to compare both assays. We collected data from 132 patients receiving a daily dose of aspirin (100 mg/day) and data from 48 patients receiving aspirin on alternate days. All Patients who received a daily dose of aspirin were studied for AA-induced platelet aggregation together with serum TxB2 levels and AA-induced TxB2 formation was also studied in 71 patients out of entire population. Consistent with recommendations in the literature, we defined HAPR by setting a cut-off point at 3.1 ng/ml for serum levels of thromboxane B2 and 20% for AA-induced platelet aggregation. According to this cut-off point, we divided our overall population into two groups: (1) TxB2 < 3.1 ng/ml and (2) TxB2 > 3.1 ng/ml. We found low agreement between such tests to identify patients displaying HAPR. Our results show that AA-induced platelet aggregation >20% identify a smaller number of HAPR patients in comparison with TxB2. A good correlation between serum TxB2 and arachidonic acid-induced TxB2 production was found (r = 0.76619). [ABSTRACT FROM PUBLISHER]

Activated platelets play a substantial role in Alzheimer's disease (AD) and atherothrombosis. Mean platelet volume (MPV) is an early marker of platelet activation, which is linked to a variety of pro-thrombotic and pro-inflammatory diseases. This study is to examine the association between platelet indices and vascular dementia (VaD) and AD. In this cross-sectional study, we investigated the levels of platelet count, MPV, and platelet distribution width (PDW) in 150 VaD patients, 110 AD patients, and 150 non-demented controls. MPV and PDW were significantly lower in patients with VaD and AD as compared with controls. The decrease in PDW for AD patients as compared with VaD patients was also significant ( p < 0.001). In addition, there was a positive correlation between Mini-Mental State Examination (MMSE) and MPV and PDW, after adjusting confounding factors ( r = 0.532 for MPV and r = 0.425 for PDW, p < 0.001 for both). Multivariate regression analysis showed that MPV and PDW were significantly associated with MMSE ( β = 0.366 for MPV and β = 0.273 for PDW, p < 0.001 for both). In conclusion, MPV and PDW were both decreased in VaD and AD. PDW levels were significantly lower in AD as compared to those in VaD. Our findings suggest that PDW in combination with MMSE scores could be potential indicators for distinguishing VaD from AD. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the associations of the mean platelet volume (MPV) high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-B type natriuretic peptide (NT-proBNP) with the development of adverse outcomes after percutaneous coronary intervention (PCI). MPV hs-cTnT and NT-proBNP were analyzed in 372 patients who underwent PCI. The primary endpoint was cardiac death. The secondary endpoint analyzed was cardiovascular events (CVE): the composite of cardiac death, myocardial infarction (MI), target vessel revascularization (TVR), ischemic stroke and stent thrombosis (ST). The median MPV hs-cTnT and NT-proBNP levels were 8.20 (IQR 7.70-8.70) fL, 0.291 (IQR 0.015-3.785) ng/mL, and 105.25 (IQR 50.84-1128.5) pg/mL, respectively. There were 21 events of cardiac death, 10 MI (including 4 events of ST), 7 ischemic strokes and 29 TVR during a mean of 25.8 months of follow-up. The Kaplan-Meier analysis revealed that the higher MPV group (>8.20 fL, median) had a significantly higher cardiac death rate than the lower MPV group (≤8.20 fL; 9.4% vs. 2.1%, log-rank: p = 0.0026). When the MPV cut-off level was set to 8.20 fL using the receiver operating characteristic curve, the sensitivity was 81% and the specificity was 53.3% for differentiating between the group with cardiac death and the group without cardiac death. This value was more useful in patients with myocardial injury (hs-cTnT ≥ 0.1 ng/mL) or heart failure (NT-proBNP ≥ 450 pg/mL). The results of this study show that MPV is a predictive marker for cardiac death after PCI; its predictive power for cardiac death is more useful in patients with myocardial injury or heart failure. [ABSTRACT FROM AUTHOR]

Platelets may be activated in hypertension (HT). Hypertensive crisis is an extreme phenotype of HT and HT-related thrombotic complications. We aimed to assess mean platelet volume (MPV) in patients with hypertensive crises. This study included 215 hypertensive urgency (HU) patients (84 male, mean age = 66 ± 15 years) and 60 hypertensive emergency (HE) patients (26 male, mean age = 68 ± 13 years), who were admitted to the emergency department with a diagnosis of hypertensive crises. Control group was composed of age- and sex-matched 39 normotensive patients. Blood samples were withdrawn for whole blood count and routine biochemical tests. Systolic blood pressure (BP) was significantly higher in the HE group than in the HU group ( p < 0.001). Median mean platelet volume (MPV) was higher in the HE group compared with HU and control groups [9.5 (Interquartile range, IQR: 8.7-10.1), 8.4 (IQR: 7.7-9.1), and 8.3 (IQR: 7.7-8.7) fl, each p < 0.001, respectively). In linear regression analysis, systolic BP ( β = 0.18, 95% confidence intervals (CI): 0.002-0.015, p = 0.007) and diabetes mellitus ( β = 0.24, 95% CI: 0.28-0.95, p < 0.001) were independently associated with MPV levels. Our findings show that MPV can be elevated in patients with HE and HU. It can be independently associated with systolic BP and diabetes mellitus. These findings imply that platelet activation contribute to the pathogenesis of thrombotic complications in hypertensive crises. [ABSTRACT FROM AUTHOR]

It has been found that in 15% of acute myocardial infarction patients' platelets generate reactive oxygen species that can be detected with luminol-enhanced chemiluminescence of platelet-rich plasma within 8-10 days after acute myocardial infarction. This increase in generate reactive oxygen species production coincides with the emergence of CD45+ platelets. The ability of platelets to carry surface leukocyte antigen implies their participation in exchange of specific proteins in the course of acute myocardial infarction. Future studies of CD45+ platelets in peripheral blood of acute myocardial infarction patients in association with generate reactive oxygen species production may provide a new insight into the complex mechanisms of cell-cell interactions associated with acute myocardial infarction. [ABSTRACT FROM AUTHOR]

Platelet-bound stromal cell-derived factor-1 (SDF-1) plays a crucial role in attachment of circulating CD34+ progenitor cells to the vascular wall, facilitating tissue healing after injury. However there is no evidence about expression of platelet-bound SDF-1 in patients with congestive heart failure (CHF). The aim of our study was to evaluate expression of platelet-bound SDF-1 and number of CD34+ progenitor cells in patients with CHF. Forty-eight patients with idiopathic dilated cardiomyopathy (DCM) and 61 patients with ischaemic cardiomyopathy (ICM) were consecutively enrolled into the study. Blood taken from 109 consecutive patients was studied for surface expression of platelet-bound SDF-1 and number of CD34+ progenitor cells by flow cytometry. The highest expression of platelet-bound SDF-1 was observed in patients with severe impairment of left ventricular systolic function compared with patients with mild or moderate impairment of left ventricular systolic function (mild vs. moderate vs. severe impairment of left ventricular systolic function: MFI ± SD: 35.6 ± 34 vs. 101.45 ± 73 vs. 124.86 ± 86.7, Kruskal-Wallis p < 0.001). Similar to platelet-bound SDF-1 number of CD34+ progenitor cells was the highest in severe impairment of left ventricular systolic function (mild vs. moderate vs. severe impairment of left ventricular systolic function: mean ± SD: 260.4 ± 177.5 vs. 580.7 ± 340.5 vs. 640.82 ± 370.6, Kruskal-Wallis p < 0.001). Platelet-bound SDF-1 expression was associated with number of circulating CD34+ progenitor cells ( r = 0.454, p < 0.001) in patients with CHF. Expression of platelet-bound SDF-1 and number of CD34+ cells were higher in patients with DCM compared with patients with ICM ( p < 0.001 for both) and inversely correlated with age and aspirin therapy. Platelet-bound SDF-1 and CD34+ progenitor cells are especially increased in patients with severe impairment of left ventricular systolic function in CHF. [ABSTRACT FROM AUTHOR]

Both the Global Registry of Acute Coronary Events (GRACE) risk score and mean platelet volume (MPV) can independently predict adverse cardiovascular disease (CVD) events in patients with acute coronary syndrome (ACS). This study was aimed at investigating whether MPV was related to the GRACE risk score and whether the combination of them could have a better performance in predicting CVD in Patients with ACS. Totally 297 ACS patients were included. MPV was measured on admission. The GRACE risk score was calculated and its predictive value alone and together with MPV was assessed, respectively. During a median period of 52 months (range, 6 to 65), 11 of the 297 subjects (3.7%) were lost to follow-up, and 132 (46.2%) had adverse CVD including 32 deaths. Both MPV and the GRACE score were higher in patients with CVD events than those without events, and the GRACE score increased with the increase of MPV. Multivariate Cox analysis demonstrated that both MPV and the GRACE score were significant and independent predictors for CVD events (HR: 1.13; 95% CI: 1.10 to 1.15; p = 0.006; HR: 1.30; 95% CI: 1.24 to 1.37; p < 0.001; respectively). The area under the ROC curve was 0.70 (95% CI: 0.64 to 0.76, p < 0.001) when the GRACE score was calculated alone, whereas it increased to 0.85 (95% CI: 0.81 to 0.90, p < 0.001) with the addition of MPV, indicating that the combination of MPV with the scoring system improved the predictive value. This study demonstrates for the first time that MPV is positively associated with the GRACE risk score and it may complement the scoring system in predicting CVD events in patients with ACS. [ABSTRACT FROM AUTHOR]

The mean platelet volume (MPV) is a laboratory marker associated with platelet function and activity. Increased MPV in thromboembolic disease is considered an important risk factor. The aim of this study was to compare the MPV and MPV/platelet count (MPV/P) ratio between deep vein thrombosis (DVT) and control subjects. We retrospectively reviewed the medical records of patients (n = 91) admitted due to newly diagnosed DVT from December 2010 to March 2012. The control group (n = 311) underwent health screening at our Hospital. Median MPV was higher in DVT patients compared to controls (8.6 fl vs. 7.9 fl, p < 0.0001). The DVT patients also had a higher MPV/P ratio compared to the control group (0.0388 fl/(109/l) vs. 0.0308 fl/(109/l), p < 0.0001). MPV was inversely correlated with platelet count in DVT patien (correlation coefficient =-0.33, p = 0.001). Receiver operator characteristic analysis revealed that an MPV cutoff value of 8.2 fl provided 70.3% sensitivity and 72.7% specificity. An MPV/P cutoff value of 0.0363 fl/(109/l) showed 60% sensitivity and 73% specificity. MPV and MPV/P ratio could be considered meaningful laboratory markers for the risk of DVT. [ABSTRACT FROM AUTHOR]

Platelet size, measured as mean platelet volume (MPV), is associated with platelet reactivity. MPV has been identified as an independent risk factor for future stroke and myocardial infarction. The aim of this study was to determine the association of MPV with the development of stoke in patients with atrial fibrillation (AF). MPV, N-terminal pro B-type natriuretic peptide (NT-proBNP), and high-sensitivity C-reactive protein (hsCRP) were analysed in 200 patients with AF (mean age 69 years; 56%% male). The primary endpoint was ischaemic stroke event. The mean MPV was 8.5 ±± 1.0 fL and the median NT-proBNP was 1916.5 (IQR 810--4427) pg/mL. The median hsCRP was 0.47 (IQR 0.32--2.46) mg/dL. There were 14 stroke events during a mean of 15.1 months of follow up. Kaplan-Meier analysis revealed that the higher tertile MPV group (≥≥8.9 fL) had a significantly higher stroke rate compared to the lower tertile MPV group (<8.0 fL) (14.7%% vs. 3.1%%, log-rank: P == 0.01). A higher MPV was an independent predictor of stroke risk after adjusting for age, gender, and other CHADS2 (congestive heart failure, hypertension, diabetes, and previous stroke or transient ischemic attack (TIA) history) score components (hazard ratio: 5.03, 95%% CI 1.05--24.05, P == 0.043) in Cox proportional hazard analysis. When the MPV cut-off level was set to 8.85 fL using the receiver operating characteristic curve, the sensitivity was 71%% and the specificity was 69%% for differentiating between the group with stroke and the group without stroke. This value was more useful in patients with a low to intermediate traditional thromboembolic risk (CHADS2 score <2). Furthermore, AF patients with an MPV over 8.85 fL had high stroke risk without anticoagulation, especially in the low thromboembolic risk group (Log-Rank <0.0001). The results of this study show that MPV was a predictive marker for stroke; its predictive power for stroke was independent of age, gender, and other CHADS2 score components in patients with AF. These findings suggest that anticoagulation may be needed in patients with a high MPV, even if they have low to intermediate traditional thromboembolic risk (CHADS2 score <2). [ABSTRACT FROM AUTHOR]

Thrombocytopenia related to Helicobacter pylori infection is a definitive subset of chronic immune thrombocytopenic purpura (ITP) but its long-term prognosis has not been evaluated extensively. The possibility of recurrence of thrombocytopenia after re-infection of H. pylori is another concern. We evaluated 8-year follow-up data for 11 patients with ITP related to H. pylori infection in a single institution. In 2001, patients with chronic ITP were evaluated for H. pylori infection at the Tokyo Metropolitan Komagome Hospital using 13C urea breath test (UBIT). Nineteen patients turned out to be positive and were treated for H. pylori infection. Platelet count 6 months after treatment revealed complete response (CR) in 10 patients and response in one patient. Eight years later, 17 of these 19 patients were re-evaluated for H. pylori infection and platelet count. Platelet counts of the 11 previous responders remained to indicate CR. Two of 13 patients re-examined by UBIT showed positive results and one of these two patients continued to keep normal platelet count. Nonetheless, the prognosis of patients who responded to eradication was excellent. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate cell maturation and the platelet production capacity of the megakaryoblastic DAMI cell line, to characterize platelet-like particles produced and to investigate the mechanisms involved in their production. DAMI cell maturation was induced by phorbol myristate acetate (PMA) and thrombopoietin (TPO). Expression levels of GATA-1, Fli-1 and NF-E2 were evaluated using real-time PCR and western blot. Platelet-like particles were characterized by the presence of GPIb and GPIIb by flow cytometry, while the soluble fragment of GPIb, glycocalicin, was detected by enzyme immunoassay. Dense and alpha granules were evaluated by mepacrine staining and thrombospondin-1 detection, respectively, and by electron microscopy. Functional capacity of platelet-like particles was studied by measuring P-selectin membrane after thrombin stimulation by flow cytometry and actin polymerization using phalloidin-FITC by immunofluorescence. We found that stimulation of DAMI cells with high concentration of PMA and TPO induced the expression of transcription factors GATA-1 and Fli-1 followed by an increase in the isoform a of NF-E2. Mature DAMI cells give rise to extensions resembling proplatelets and later, produce platelet-like particles expressing GPIIb and GPIb on their surface and containing dense and alpha granules, which were confirmed by electron microscopy. Platelet functionality was demonstrated by the increase in P-selectin membrane expression after thrombin stimulation and by their ability to spread on fibrinogen matrices. DAMI cell line induced to differentiate into mature megakaryocytes is able to produce functional platelets providing a suitable model to study the mechanisms involved in platelet generation. [ABSTRACT FROM AUTHOR]

High expression of the collagen receptor, α2β1 integrin, on platelets ofITGA2807T-allele carriers has been identified as a risk factor for thromboembolic conditions, and α2β1 inhibitors are considered to be potential therapeutic agents. In 59 genotyped individuals, we measured α2 expression levels on platelets and analyzed platelet adhesion to collagen under flow conditions. A sulfonamide-type small-molecule inhibitor of α2β1 integrin decreased average platelet adhesion in individuals with the C/T807T genotype but not in those harboring C807C. Thus, genotype can be used to select a human subpopulation that has the highest probability of showing a positive response to α2β1 inhibitors. [ABSTRACT FROM AUTHOR]

Point-of-care platelet monitoring is increasingly used in cardiac patients treated with antiplatelet agents. The validity of a new assay needs to be evaluated not only for reproducible data in clinical samples, but also for other pre-analytical conditions that may influence measurements. The aim of this study was to evaluate the influence of a pneumatic tube system (PTS) for specimen transport on impedance platelet aggregometry. We evaluated 50 consecutive patients scheduled for coronary artery bypass surgery under oral therapy with 100 mg/d acetylsalicylic acid (aspirin). In each patient, three blood samples for platelet function analysis were taken before induction of anesthesia. The first sample was measured in the operating room (OR) area and designated as the reference value. The second sample was again measured by the same operator in the OR area using a random PTS transport. The third sample was sent to the central laboratory by PTS where it was measured by a local technician. Platelet function was assessed in whole blood by impedance aggregometry with a Multiplate™ analyzer using thrombin-related activation peptide (TRAP test) and arachidonic acid (ASPI test) (Dynabite GmbH, Munich, Germany). Mean ± SD for TRAP test was 1009 ± 196 in the reference measurement. Bias ± 95% limit of agreement between the reference measurement and a second measurement for TRAP test were 126 ± 284 (n = 25) for untransported and 181 ± 316 (n = 25) for PTS transported samples. In the reference measurements, 48/50 (96%) of TRAP values were within the normal range. After PTS transport, 35/50 (70%) of TRAP measurements in the central laboratory were within the normal range (p < 0.001). Mean ± SD for ASPI test was 175 ± 137. Bias ± 95% limit of agreement for ASPI test were 12 ± 109 (n = 25) for untransported and 68 ± 250 (n = 25) for PTS transported samples. In the reference measurements, 7/50 (14%) ASPI values were above the cut-off level and defined as reduced aspirin responsiveness. After PTS transport, only 1/50 (2%) of the patients showed reduced aspirin responsiveness in the central laboratory measurements (p = 0.031). In conclusion, PTS transport had a significant influence on platelet function testing by the Multiplate™ analyzer. Significantly fewer test results indicated normal platelet function in TRAP test and reduced aspirin responsiveness in ASPI test after PTS transport. Therefore, clinical decisions regarding platelet function and aspirin responsiveness should not be based on blood specimens transported by a PTS system. [ABSTRACT FROM AUTHOR]

We have recently suggested that platelets could be used as a model for neuronal receptors. In this paper we have investigated γ-aminobutyric acid (GABA) metabolism and GABA receptors in platelets and in cultured neurons to see whether platelets' GABA mimics neuronal GABA receptor activities. We used the ELISA technique for detecting the GABA concentration in platelet rich plasma and cultured neurons. The functional effects of GABA and its receptor ligands on platelets were determined using an aggregometer. We found that the GABA concentration is 30% lower in platelets than in neurons and in both preparations GABA was metabolized by GABA transaminase (GABA-T). GABA potentiated calcium dependent platelet aggregation with a higher value in washed platelets suspension (WPS) then in platelet rich plasma (PRP). This effect was inhibited by benzodiazepines, calcium channel blockers and the selective phosphoinositide 3-kinase antagonist Wortmannin. GABA neurotransmission is involved in most aspects of normal brain function and can be perturbed in many neuropathologic conditions. We concluded that platelets could be further developed to be used as a peripheral model to study neuronal GABAergic function and its abnormality in diseases such as epilepsy and schizophrenia. Furthermore our results indicated that PI3-kinase is involved in calcium dependent GABA induced platelet aggregation as this synergistic effect is inhibited by Wortmannin in dose dependent manner. [ABSTRACT FROM AUTHOR]

Platelet aggregation and microaggregate formation were measured in samples of stirred whole blood by flow cytometry. Blood samples were stirred in a multi-sample agitator with ADP, fixed and labelled with a platelet-specific CD42a-FITC fluorescent antibody. The blood was then diluted and applied directly to a flow cytometer. Platelets were identified using a gating procedure based on their expression of CD42a and then quantified. Aggregation was monitored as a fall in the number of single platelets. Both reversible and irreversible aggregation responses to ADP were determined and these were found to correlate directly with aggregation responses determined using a well-established single platelet counting technique using the Ultra-Flo 100 Whole Blood Platelet Counter. We found from flow cytometry that ADP-induced aggregation was coupled with a transient formation of platelet microaggregates over the initial 60 s following ADP addition. Assessment of single platelet loss by flow cytometry was found to be a reliable way of monitoring aggregation responses and provided new information on rapid microaggregate formation in ADP-stimulated blood. [ABSTRACT FROM AUTHOR]

The principal physiological function of platelets is to promote haemostasis but they also contribute to thrombosis and atherogenesis. Platelet volume is a marker and possibly a determinant of platelet function in that large platelets are more active than normal sized platelets. Mean platelet volume (MPV), a measure of platelet size, reflects changes in either the level of platelet stimulation or the rate of platelet production. For these reasons, we have developed a sensitive instrument to measure platelet volume, which we believe is more reliable and specific than previously used instruments. It is based on a computer - interfaced Coulter Thrombocytometer and a pulse analyser including a high - speed baseline restorer. We have developed a reproducible method to assay MPV and from the histogram derived the median (MED) and the skewness (SK) values. We have looked at the effects of anticoagulant used and time elapse prior to assay. A normal range has been established for MPV which correlates directly with MED and inversely with SK. The MPV decreases with age but there is no difference between genders. We have demonstrated a negative correlation between whole blood platelet number and MPV and MED, and a direct relationship with the SK of the histogram of the platelet volume. [ABSTRACT FROM AUTHOR]

The article reports that the blood platelets play a significant role in the haemostatic mechanisms of the human body. It states that reduction or increase in platelet function, has direct impact on the health of individuals, and may lead to heart attack and stroke, and highlights the importance of analyzing blood platelet count in clinical practice. It discusses the use of light transmission aggregometry (LTA) technology in measuring platelet function.